The webs that spiders(蜘蛛) build to catch insects seem weak. However, the strength of spider thread is greater than steel. Webs can even stand up to very strong storms.
In each spider web, some threads are sticky(粘的), but some are not. When a spider is moving on the web, it will not step on the sticky threads. After a time the silk will lose its stickiness and become unable to catch insects. Then, spiders usually eat their own web.
Now a team of scientists has worked out why the spider web is so strong. It is not just the strength of the thread, but the clever design of the web. The key to a web’s success is its ability to keep its shape and strength even after some of the threads break, say scientists at the Massachusetts Institute of Technology. The scientists found the thread itself has the ability to become softer or harder. So it can hold different types of heavy things.
In tests, scientists used three other strong materials(材料) made into the same webs. The spider thread was six times stronger than any other material. More surprisingly, when the scientists took away up to 10 percent of the threads from different places, the web didn’t become any weaker. Actually, it became up to 10 percent stronger.
The spider web’s clever design gives scientists many new ideas. The findings could help design safer buildings and even a new type of strong material. “It’s a really good chance,” said Markus Buehler, a professor at MIT. “It may give us some new ideas for engineering.”

According to the passage, the spider web is strong because       .
a. the spider’s thread is sticky
b. the thread has a lot of strength
c. the web has a clever design
d. the web can keep the strength forever

A．ab

B．ac

C．bc

D．bd

In paragraph 4, the scientists’ tests show that       .

A．the spider’s thread is stronger than the other three materials

B．the spider’s thread is the strongest material in the world

C．the spider’s thread can be as soft or hard as it needs to be

D．taking away some spider thread makes the web weaker

From the last paragraph, we learn that       .

A．people can use spider webs to build houses

B．the findings give people new ideas for buildings

C．there are many reasons why the spider web is so strong

D．Professor Buehler will make a new type of material

Which of the following would be the best title for the passage?

A．How spiders catch insects

B．How spiders design webs

C．Spiders are clever designers

D．Webs are stronger than steel

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