根据文章内容，从下列AF选项中选出能概括每一段主题的最佳选项-优题课

The reason why science exists is to improve our lives. Sometimes science can ruin our small guilty pleasures we nature to be happier, though. These four little truths are just some of those.
Sleeping with pets is a good way to catch the plague(瘟疫), or some other bacterial infections, as is claimed in the study done in February 2011 in Emerging Infectious Diseases magazine. The study shares a case of a nine-year-old boy whose cat caught the plague and gave it to its owners while they were sharing a bed. A regular visit to the vet can greatly reduce the risk of your pet catching any disease that may infect the owner as well.
A recent study done on 200,000 people has shown that vitamin supplements do nothing to improve our lives, and what is worse—they actively increase our death risk. This conclusion from 2010 was so unbelievable that it made researchers do even more studies. Each study had the same result. People who choose vitamin supplements over fruit and vegetables are the same as people who choose to eat a burger over a healthy salad.
People who use the solarium(日光浴室)experience certain changes to their brains that are very similar to many caused by drug addiction. According to a study, our brain can in fact recognize the difference between the natural UV light and the solarium.
Long exposure to artificial light during the night is directly linked to a higher risk of breast cancer, obesity and depression. Exposure to artificial light before sleeping disturbs the natural biorhythms(生物节奏)of our bodies, which leads to restriction on the hormone(荷尔蒙)melatonin, which is the hormone that helps us fall asleep.

Title: Four scientific_______
Passage outline	Supporting details
Sharing bed with your pet is a terrible idea	You will probably be infected with______. To reduce such risk, you should take your pet to visit the vet______.
Be______about vitamin supplements	Vitamin supplements actively increase the risk of______.
You can become_____ to solariums	The solarium may bring about changes to the______just like drugs do.
_____long exposure to artificial lights	You are likely to_____from breast cancer, obesity and depression after long exposure to artificial lights. The natural biorhythms of your bodies will be disturbed and you will find it not______to fall asleep.

An apprenticeship is a form of on-the-job training that combines workplace experience and classroom learning. It can last anywhere from one to six years, but four years is typical for most. An apprentice spends the majority of the time in a workplace environment learning the practical skills of a career from a journeyman--someone who has done the job for many years. The rest of the apprentice's time is spent in a classroom environment learning the theoretical skills the career requires. Being an apprentice is a full-time undertaking.
One of the advantages of apprenticeship is that it does not cost apprentices anything. The companies that hire them pay for school. What's more, it offers apprentices an "earn while you learn" opportunity. They usually start out at half the pay of a journeyman, and the pay increases gradually as they move further along in the job and studies. Near the end of the apprenticeship, their wages are usually 90 percent of what a journeyman would receive. Apprenticeship also pays off for employers. It can offer employers a pool of well-trained workers to draw from.
Despite the advantages, apprentices are usually required to work during the day and attend classes at night, which leaves little time for anything else. Sometimes, they might be laid off(下岗) if business for the employers is slow.
Once they have completed the apprenticeship and become journeymen, they receive a nationally recognized and portable certification and their pay also increases again. Some journeymen continue employment with the companies they apprenticed with; others go onto different companies or become self-employed contractors.

The basics of infrastructure design
It is rightly pointed out various intellectuals that the lifestyle of today is vastly different from that of the earlier times especially in terms of its pace. Lifestyle of today is remarkablyfast paced and so in order to catch up with such a pace of life, the adoption of smart and time saving methods is of real significance. Well, the highways have certainly contributed in this direction and have made our lives a lot easier. Thanks to the modern flyovers and expressways, a single route can be accessed by twice the number of vehicles at the same time.
These facilities and supplies have made our lives double free but it needs to be realized that designing and constructing it is a very complex and a long process. You have to hold fast to the various rules of designing, government standards and most importantly, their safety and usability for the people. In the end it is a joint effort of a number of skilled engineers, scientists and statisticians. The material that is used in the construction is finalized after it undergoes certain tests for evaluating their qualities like hardness, roughness, thickness and all that is required.
Some of the points you have to take care of while laying an infrastructure design are as follows:
The basic layout (布局) of the road — At this level of planning, various civil engineers have meetings to figure out the basic requirements of the road like thickness of the asphalt (沥青), the size of lanes, distance to be covered, degree of curves and much more. These fundamental points help them decide the further line of action.
The prior steps — Before any work is stated over the basic plan layout, there are various preparations to be made like placing road signs, the removal of trees that may prove to be dangerous in the event of a storm or other natural causes, the positioning of fire hydrants (消防栓) based on special designs to be useful when required, etc.
Inclusion of safety barriers — The safety barriers are placed on almost all roads and highways that are made over or near to rivers and cliffs. These barriers keep the vehicles from moving into the traffic in instances of accidents. These should also be designed in advance of placing them on a road and the design should be such that it makes minimum impact upon the people sitting in the car. These include supplies like side rails and light poles.
Asphalt pavement marking — It is the process of using a reflective material to indicate various important points on the road like lanes, turns, passing areas, two way and one way roads.
Though the smooth and wide highways constructed in big cities seem to be very attractive for the drivers, the ease of use is also the cause of accidents. Cars rushing at extremely high speeds and insecure change of lanes are a common sight on the highways. With the help of novel infrastructure design engineers, we can make the best possible use of highways. If these are designed properly and sign boards are placed at the required points, a number of road accidents can be avoided.

The basics of infrastructure design
Reason for construction of infrastructure	Infrastructure must_________ the demands of today’s fast-paced lifestyle.
Challenges of design and _________	Various rules, standards, safety and usability should be taken into careful consideration.
Skilled engineers, scientists and statisticians have to work hard _________.
Materials must be_________ to ensure their qualities.
Points to follow	Various engineers meet to make sure about fundamental _________ of the road.
Things like __________ trees that are potentially dangerous must be done before construction.
Safety barriers should be carefully_________ before being placed to prevent accidents.
Material that can _________ light should be used to marks on the pavement.
Possible problems and solutions	Smooth and wide highways may _________accidents.
Highways should be designed properly and sign boards _________ at the required points.

It was a winter morning, just before Christmas, while most people were warming up their cars, my husband, Trevor, had to ride his bike 4 kilometers away from home to work. On his (arrive), he parked his bike outside the back door usual. After 10 hours of labor, he returned to find his bike gone, was our only transport. Trevor used it to get to work, and also the bike was used (get) groceries, saving us from having to walk long distances from where we live. I was so sad I wrote to the newspaper and told them our story. Shortly after that, several people in our area offered to help. One wonderful stranger even bought a bike, and then called my husband to fetch . Once again my husband had a way to get to and his job. It really is honor that a complete stranger would go out of their way for someone they have never met before. People say that a smile can (pass) from one person to another, but acts of kindness from strangers are even more so. This experience has had a spreading effect on our lives because it (strong) our faith in humanity. And it has influenced us to be more mindful of ways we, too, can share with others.

In the days when an ice cream cost much less, Tom, ___ __8-year-old boy, entered a hotel coffee shop __sat at a table. A waitress put a glass of water in front of him. “How much is an ice cream?” “Fifty-cents,” replied the waitress. The little boy pulled ___ right hand out of the pocket and studied a number ofin it. “How much is a dish of plain ice cream?” he asked. Some people were now waiting for her service and the waitress grew a bit __ _ (patience). “Thirty-five cents.” she said ___(rude). The little boy carefully counted the coins _____.“I will have a plain ice cream,” he said. The waitress walked _ __ __. The boy finished the ice cream, paid the cashier and left. It was not long __the waitress came back and then she began to wipe down the table and suddenly was surprised at what she saw. There, _ __(place) neatly beside the empty dish, were two nickels and five pennies — her tip!