题目内容：

To many web-building spiders, most of whom are nearly blind, the web is their essential window on the world: their means of communicating, capturing prey, meeting mates and protecting themselves. A web-building spider without its web is like a men cast away on an island of solid rock，totally out of touch and destined to starve to death. So important is the web to an orb-web spider's survival that the animal will continue to construct new webs daily even if it is being starved. For 16 days the starving spider builds completely normal webs. Then, as the animal gets scrawnier, it constructs a wider-meshed （网孔、网眼）web using fewer strands（线）. Such webs would only trap larger prey, which is more economical from the perspective of a starving spider. The spider stores energy by recycling web protein. It simply eats its own web each evening and reuses it to produce new silk. In studies with radioactivity, labeled materials, it was found that 95 percent of web protein reappears in the next day web. Most of the energy needed for web-building is used in walking over the strands as they are laid down. Scientists are impressed by the adaptability of the spider's highly preprogrammed brain, which is larger for its size than the brain of any other invertebrate（无脊推动物）. If web-building is interrupted, or if some of the existing strands are destroyed, the spider simply goes back to see where the web is left off and then finishes building a normal web. One spider will finish building the incomplete web of another.

1.Which of the following best expresses the main ideas of the passage?

A. Secrets of Spiders' Adaptability

B. Importance of Webs to Spiders

C. Secrets of the Spiders' Life

D. Spiders' Highly Preprogrammed Brain

2.According to the passage, which of the following statements is TRUE?

A. Most spiders will stop conducting webs when hungry.

B. One Web-building spider usually conducts one web. 

C. Web-building spiders will probably die without their webs. 

D. Web-building spiders have good eyesight.

3.The underlined word “scrawnier” in the second paragraph probably means ______. 

A. weaker but good-looking

B. fatter and stronger

C. nice and healthier

D. thinner and bony

4.A spider's ability to finish an incomplete web proves that ______.

A. it has a highly preprogrammed brain

B. it reuses its web protein to reproduce new silk

C. the web is everything for a spider

D. it is able to rebuild a destroyed web