阅读下面短文，请从短文后所给各题的4个选项(A、B、C、D)中选出一个最佳选项。 It is said that when the mighty ruler Genghis Khan conquered Asia, his soldiers were protected from enemy arrows by very special clothing. These leather garments were woven with one of the strongest materials then known to humans — spider silk! Eight hundred years later, scientists still can't make thread more durable (耐用的) than the stuff spiders use to make webs. But biologists trying to copy nature's strongest fiber are making great progress. The U.S. Army plans to use one of the Great Khan's tricks: making bulletproof vests woven with artificial spider silk. What makes spider silk so remarkable is its unique combination of strength and stretch. Spider silk is as strong as the fiber now used to make bulletproof vests, but far more elastic（有弹性的）. The web of golden silk spider is strong enough to trap a bird. Researchers have figured out that a web woven of spider silk the thickness of a pencil could stop a plane in midair! "When you think about the size and speed of flying bee, the web that catches it has to be able to absorb a lot of energy,"says Jean Herbert, an Army scientist in Natick, Massachusetts. Herbert is researching ways to use the tough fiber in everyday objects. Among the possibilities: jeans that don't wear out, car and truck bumpers that resist dents, and bridges whose structures can withstand earthquakes. Unlike silkworms, spiders cannot be raised on farms. (One reason: they tend to eat one another!) So scientists are inventing ways of making spider silk without spiders. The ability to spin a web is controlled by certain genes inside the cells of spiders. Researchers at two chemical companies have made copies of these genes and put them into certain easy-to-grow bacteria (细菌). The scientists’ goal: bacteria that can turn out spider silk. Transplanting spider genes is a sticky business. The genes don't always act exactly the way they would in a living spider, so the silk is not as strong or elastic as the real stuff. For now, the surest silk — production method is the one that Genghis Khan supposedly used-spiders themselves. "I never step on spiders”, says chemist John O'Brien. "I have too much respect for them."