Can people change their skin color without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin color.
The gene comes in two versions, one of which is found in 99 per cent of Europeans. The other is found in 93 to 100 per cent of Africans, researchers at Pennsylvania State University report in the latest issue of Science.
Scientists have changed the color of a dark-striped zebrafish（斑马鱼） to uniform gold by inserting a version of the pigment (色素) gene into a young fish. As with humans, zebrafish skin color is determined by pigment cells, which contain melanin (黑色素). The number, size and darkness of melanin per pigment cell determine skin color.
It appears that, like the golden zebrafish, light-skinned Europeans also have a mutation (变异) in the gene for melanin production. This results in less pigmented skin.
However, Keith Cheng, leader of the research team, points out that the mutation is different in human and zebrafish genes.
Humans acquired dark skin in Africa about 1.5 million years ago to protect bodies from ultra-violet rays of the sun (太阳光紫外线), which can cause skin cancer.
But when modern humans leave Africa to live in northern latitudes, they need more sunlight on their skin to produce vitamin D. So the related gene changes, according to Cheng.
Asians have the same version of the gene as Africans, so they probably acquired their light skin through the action of some other gene that affects skin color, said Cheng.
The new discovery could lead to medical treatments for skin cancer. It also could lead to research into ways to change skin color without damaging it like chemical treatment did on Michael Jackson.The passage mainly tells us that ________.
| A．people can not change their skin color without any pain |
| B．the new discovery could lead to research into ways to change skin color safely |
| C．pop king Michael Jackson often changed his skin color as he liked |
| D．scientists have found out that people’s skin color is determined by the gene |
It can be inferred from the passage that ________.
| A．nowadays people who want to change their skin color have to suffer a lot from the damage caused by the chemical treatment |
| B．Europeans and Africans have the same gene |
| C．the new discovery could help to find medical treatments for skin cancer |
| D．there are two kinds of genes |
Scientists have done an experiment on a dark-striped zebrafish in order to ________.
| A．find the different genes of humans’ |
| B．prove the humans’ skin color is determined by the pigment gene |
| C．find out the reason why the Africans’ skin color is dark |
| D．find out the ways of changing people’s skin color |
The reason why Europeans are light-skinned is probably that _____
| A．they are born light-skinned people |
| B．light-skinned Europeans have mutation in the gene for melanin production |
| C．they have fewer activities outside |
| D．they pay much attention to protecting their skin |
The writer’s attitude towards the discovery is ________.
| A．neutral | B．negative | C．positive | D．unconcerned |
Friendships between Americans can be close and real, yet disappear soon if situations change. Neither side feels hurt by this. Both may exchange Christmas greetings for a year or two, perhaps a few letters for a while — then no more. If the same two people meet again by chance, even years later, they pick up the friendship. This can be quite difficult for us Chinese to understand, because friendships between us flower more slowly but then may become lifelong feelings, extending (延伸) sometimes deeply into both families.
Americans are ready to receive us foreigners at their homes, share their holidays, and their home life. They will enjoy welcoming us and be pleased if we accept their hospitality (好客) easily.
Another difficult point for us Chinese to understand Americans is that although they include us warmly in their personal everyday lives, they don’t show their politeness to us if it requires a great deal of time. This is usually the opposite of the practice in our country where we may be generous with our time. Sometimes, we, as hosts, will appear at airports even in the middle of the night to meet a friend. We may take days off to act as guides to our foreign friends. The Americans, however, express their welcome usually at homes, but truly can not manage the time to do a great deal with a visitor outside their daily routine. They will probably expect us to get ourselves from the airport to our own hotel by bus. And they expect that we will phone them from there. Once we arrive at their homes, the welcome will be full, warm and real. We will find ourselves treated hospitably(好客).
For the Americans, it is often considered more friendly to invite a friend to their homes than to go to restaurants, except for business matters. So accept their hospitality at home!The writer of this passage must be ______.
| A．an American | B．a Chinese | C．a professor | D．a student |
Which of the following statements is TRUE according to the passage?
| A．Friendships between Americans usually extend deeply into their families. |
| B．Friendships between Americans usually last for all their lives. |
| C．Americans always show their warmth even if they are very busy. |
| D．Americans will continue their friendships again even after a long break. |
From the last two paragraphs we can learn that when we arrive in America to visit an American friend, we will probably be ______.
| A．warmly welcomed at the airport |
| B．offered a ride to his home |
| C．treated hospitably at his home |
| D．treated to dinner in a restaurant |
The underlined words “generous with our time” in Paragraph 3 probably mean ______.
| A．strict with time | B．serious with time |
| C．careful with time | D．willing to spend time |
A suitable title for this passage would probably be “______”.
| A．Friendships between Chinese |
| B．Friendships between Americans |
| C．Americans’ hospitality |
| D．Americans’ and Chinese’s views of friendships |
Franz Schubert was a well-known musician in the world. But he lived a very hard life and often went hungry. One day, being very hungry, he went into a small restaurant in Vienna, hoping he might meet some friends there. He looked around and saw nobody he could borrow any money from. Then his eyes fell on a paper on one of the tables. In it was a little poem. He took the paper with the poem. After he composed a piece of music for the poem, he took his work to the owner of the restaurant. He only received a dish of beef and potato for it. thirty years after his death, this manuscript(手稿) by Schubert was sold for 40 00c francs. it was his famous berceuse(摇篮曲).Schubert often
| A．had his meal in restaurants |
| B．looked for his friends there |
| C．ate beef and potato there |
| D．had not enough food to eat |
Schubert went into a restaurant because he thought
| A．the owner might give him some food |
| B．he could eat the food without money |
| C．some friends of his might be there and lend him some money |
| D．he could write his famous berceuse there |
From the passage we didn't know that____________.
| A．where Schubert composed his famous berceuse |
| B．why Schubert composed his famous berceuse |
| C．whether it was hard for Schubert to make a living |
| D．who bought his famous berceuse for 40 000 francs |
The best title for the passage should be_________.
| A．the hard life of Schubert |
| B．Schubert and restaurant owner |
| C．Franz Schubert in a hotel |
| D．Franz Schubert and his berceuse |
in order to know a foreign language thoroughly(完全地), four things are necessary. Firstly, we must understand the language when we hear it spoken. secondly, we must be able to speak it ourselves, with confidence(自信) and without hesitation(犹豫). Thirdly, we must do much reading. Finally, we must be able to write it. We must be able to make sentences that are correct in grammar.
There are no shortcuts to succeed in language learning. A good memory is a great help, but it is not enough only to memorize the rules from a grammar book. it is not much learning by heart long lists ( 一览表 ) of words and their meanings, studying the dictionary and so on. We must learn by using the language. If we are pleased with a few rules we have memorized, we are not really learning the language. We must "learn through use". Practice is important. We must practice speaking and writing the language whenever we can. the most import things to learn a foreign language are
| A．understanding and speaking |
| B．listening,speaking,reading and writing |
| C．writing and understanding |
| D．memorizing and listening |
Someone hears and writes English very well, but he speaks it very badly. This is because_____________.
| A．he doesn’t understand the language when he hears it spoken |
| B．he doesn’t have a good memory. |
| C．he always remembers lists of words and their meanings |
| D．he often hesitates to practice speaking it. |
Which is the most important in learning a foreign language?
| A．a good memory. | B．speaking. |
| C．practice. | D．writing. |
“Learn though use” means___________.
| A．we use a language in order to learn it |
| B．we learn a foreign language in order to use it |
| C．we can learn a language well while we are keeping using it |
| D．both b and c. |
Have you ever wondered why birds sing? Maybe you thought that they were just happy．After all，you probably sing or whistle when you are happy．
Some scientists believe that birds do sing some of the time just because they are happy．However，they sing most of the time for a very different reason．Their singing is actually a warning to other birds to stay out of their territory
Do you know what a “territory” is? A territory is an area that an animal，usually the male，claims(声称)as its own．Only he and his family are welcome there．No other families 0f the same species(物种)are welcome．Your yard and house are your territory where only your family and friends are welcome．If a stranger should enter your territory and threaten you，you might shout．Probably this would be enough to frighten him away．
If so，you have actually scared the stranger away without having to fight him．A bird does the same thing。But he expects an outsider almost any time，especially at nesting(筑巢) season．So he is screaming all the time，whether he can see an outsider or not This screaming is what we call a bird’s song，and it is usually enough to keep an outsider away．
Birds sing loudest in the spring when they are trying to attract a mate and warn others not to enter the territory of theirs．
You can see that birds have a language all their own．Most of it has to do with attracting mates and setting up territories．Some scientists believe that most of the time birds’ singing is actually．
| A．an expression of happiness |
| B．a way of greeting |
| C．an expression of anger |
| D．a way of warning |
What is a bird’s “territory”?
| A．A place where families of other species are not accepted． |
| B．An area which a bird considers to be its own |
| C．an area for which birds fight against each other． |
| D．A place where a bird may shout at the top of its Voice． |
Why do birds keep on singing at nesting season?
| A．Because they want to invite more friends |
| B．Because their singing helps get rid of their fears． |
| C．Because they want to find outsiders around． |
| D．Because their singing helps frighten outsiders away． |
Nobody likes staying at home in a public holiday, especially when the weather is fine. Last august we decided to spend the day in the country. The only difficulty was that millions of other people had exactly the same idea. We moved out of the city slowly behind a long line of cars. But at last we came to a quiet country road and after some time, stopped at a lonely farm. We had brought plenty of food with us and we got it out of the car. It was very peaceful in the cool grass until we heard ringing at the top of the hill. What we saw made us pick up our things and run back to the car as quickly as possible. There were about two hundred sheep coming towards us down the path. Nobody likes staying at home on a public holiday because ________.
| A．the weather is especially fine that day |
| B．everyone is afraid of being busy at home |
| C．he feels too crowded at home that day |
| D．each wants to have a good time in the country |
The family stopped at a lonely farm__________.
| A．to watch sheep | B．to have a meal |
| C．to visit someone | D．to find something |
They ran to their car_________.
| A．to hide themselves |
| B．to enjoy their dinner |
| C．so as not to be in the way |
| D．to get their guns and shoot at the sheep |
Which of the following is true?
| A．the road to the country is very busy on a public holiday. |
| B．the cars were too many to move that day. |
| C．seeing 200 sheep coming, they were very afraid. |
| D．that day they didn’t have any meal. |