职称英语理工类b级:2017职称英语理工类B阅读试题4

Night of the Living Ants

　　When an ant dies，other ants move the dead insect out of the nest．This behavior is interesting to scientists，who wonder how ants know for sure and so soon that another ant is dead．

　　Dong-Hwan Choe，a scientist at the University of California found that Argentine ants have a chemical on the outside of their bodies that signals to other ants．"I'm dead．take me away．"

　　But there's a twist to Choe's discovery．These ants ave a little bit like zombies(僵尸)．Choe says that the living ants，not just the dead ones，have this death chemicals．In other words．While an ant crawls around，perhaps in a picnic or home，it's telling other ants that it's dead．

　　What keeps ants from hauling away the liring dead?Choe found that Argentine ants have two additional chemicals on their bodies，and these tell nearby ants something like，"Wait-I'm not dead yet，"So Choe's research turned up two sets of chemical signals in ants：one says，"I'm dead．"the other set says，"I'm not dead yet．"

　　Other scientists have tried to figure out how ants know when another ant is dead． If an ant is knocked unconscious，other ants leave it alone until it wakes up．That means ants know that unmoving ants can still be alive．

　　Choe suspects that when an Argentine ant dies，the chemical that says"Wait-I'm not dead yet" quickly goes away.Once that chemical is gone，only the one that says"I'm dead"is left．"It's because the dead ant no longer smells like a living ant that it gets carried to the graveyard(墓地)，not because its body releases new unique chemicals after death，"said Choe． When other ants detect the"dead"chemical without the"not dead yet"chemical，they haul away the body． This was choe's hypothesis(假设)．

　　To test his hypothesis，Choe and his team put different chemicals on Argentine ant pupae(蛹). When the scientists used the"I'm dead"chemical，other ants quickly hauled tbe treated pupae away. When the scientists used the"Wait-I'm not dead yet"chemicals，other ants left the treated pupae alone.Choe believes this behavior shows that the"not dead yet"chemicals override(优先于) the"dead"chemical when picked up by adult ants． And that when an ant dies，the"not dead yet"chemicals fade away．Other nearby ants then detect the remaining"dead"chemical and remove the body from the nest．

　　36．What is meant by"death chemical"mentioned in paragraph 3?

　　A．A chemical that contains poison．

　　B．A chemical that causes death．

　　C．A chemical that announces death．

　　D．A chemical that prevents death．

　　37．Which of the following statements is NOT true of ants?

　　A．Ants know very soon that another ant is dead．

　　B．When an ant is dead，others move its body out of the nest．

　　C．If an ant is unconscious，it is moved out of the nest．

　　D．Living ants have the"I'm dead"chemical on their bodies．

　　38．According to Choe's hypothesis，___________.

　　A．an ant still smells like a living when it dies

　　B．the"I am dead"chemical leaves the ant's body when it dies

　　C．the"I am not dead yet"chemical is left when an ant dies

　　D．the"I am not dead yet"chemical leaves the ant's body when it dies

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