请阅读 Passage 1，完成 21~25 小题。

　　An electric signal can trick a monkey’s brain into believing the animal’s finger has been touched. Touch something, and your brain knows. The hand sends signals to the brain to announce contact was　made. But that feeling of touch may not require making actual contact, tests on monkeys now show. Zapping　brain cells can fool the animal into thinking its finger has touched something. A person who has lost a limb or become paralyzed may need an artificial limb to complete everyday tasks. But such patients may not truly feel any objects they hold. The new findings point toward one day creating a　sense of touch in those who use such artificial limbs. Psychologist Sliman Bensmaia of University of Chicago　worked on the new tests. His team’s findings appeared on October 14 in the Proceedings of the National　Academy of Sciences of the United States of America. The sense of touch is crucial to everyday tasks: People without it may have difficulty cracking an egg, lifting a cup or even turning a doorknob. That’s why restoring it is a major goal for designers of artificial limbs. In their new study, Bensmaia and his co-workers worked with rhesus monkeys (恒河猴). The scientists　implanted electrodes (电极)--- small devices that can detect and relay an electrical signal—into the animals’ brains. The scientists used the electrode data to identify which neurons had become active. Then the scientists　used the implanted electrodes to zap those same neurons. And the monkeys reacted as though their fingers had　been touched. In fact, they hadn’t. The monkeys couldn’t use words to tell the scientists what they had felt. Instead, they communicated by　looking in a particular direction—just as when they had really been touched. The new findings show how touch-sensitive devices could be built. The new study also offers “a nice clear　pathway” for figuring out how to restore a sense of touch to an amputee(被截肢者) or someone with a injury of　spinal cord. The study shows how artificial limbs might be connected to the brain so that a person can “feel” with such　a prosthesis (假肢). But such a supersensory device doesn’t exist yet and scientists have a lot of work to do　before people will benefit from it. Researchers must first figure out whether the electrodes would work in　people in the same way they do in monkeys. “I think the foundation is laid for human trials,” Bensmaia said. 21.What does the underlined word “it” refer to?

　　A. The sense of touch B. An artificial limb

　　C. The turning of a doorknob D. The lifting of a cup

　　22.Bensmania tested monkeys to prove that the feeling of touch _____. A. is important to everyday tasks

　　B. may not require making actual contact

　　C. is a problem of life and death

　　D. may be a challenge for designers of artificial limbs. 23.Monkeys tell researchers their sense of touch by _____. A. putting up one of their fingers B. making their brain cells active

　　C. looking in a particular direction D. mimicking natural signals in the brain

　　24.The last sentence of the text suggests humans _____. A. will use touch-sensitive devices B. will test monkeys soon

　　C. lay foundations for monkey trials D. will be tested on the electrodes

　　25.The passage is mainly about _____. A. restoring a sense of touch B. fooling a clever monkey

　　C. making new artificial limbs D. sending a signal with a touch