5．When a leafy plant is under attack，it doesn't sit quietly．Back in 1983，two scientists，Jack Schultz and Ian Baldwin，reported that young maple trees getting bitten by insects send out a particular smell that neighboring plants can get．These chemicals come from the injured parts of the plant and seem to be an alarm．What the plants pump through the air is a mixture of chemicals known as volatile organic compounds，VOCs for short．
Scientists have found that all kinds of plants give out VOCs when being attacked．It's a plant's way of crying out．But is anyone listening？Apparently．Because we can watch the neighbors react．
Some plants pump out smelly chemicals to keep insects away．But others do double duty．They pump out perfumes designed to attract different insects who are natural enemies to the attackers．Once they arrive，the tables are turned．The attacker who was lunching now becomes lunch．
In study after study，it appears that these chemical conversations help the neighbors．The damage is usually more serious on the first plant，but the neighbors，relatively speaking，stay safer because they heard the alarm and knew what to do．
Does this mean that plants talk to each other？Scientists don't know．Maybe the first plant just made a cry of pain or was sending a message to its own branches，and so，in effect，was talking to itself．Perhaps the neighbors just happened to"overhear"the cry．So information was exchanged，but it wasn't a true，intentional back and forth．
Charles Darwin，over 150 years ago，imagined a world far busier，noisier and more intimate（亲密的） than the world we can see and hear．Our senses are weak．There's a whole lot going on．
32．What does a plant do when it is under attack？D
| A．It makes noises． | B．It gets help from other plants． |
| C．It stands quietly． | D．It sends out certain chemicals． |
33．What does the author mean by"the tables are turned"in paragraph 3？A
A．The attackers get attacked．
B．The insects gather under the table．
C．The plants get ready to fight back．
D．The perfumes attract natural enemies．
34．Scientists find from their studies that plants canB．
A．predict natural disasters
B．protect themselves against insects
C．talk to one another intentionally
D．help their neighbors when necessary
35．What can we infer from the last paragraph？C
A．The world is changing faster than ever．
B．People have stronger senses than before．
C．The world is more complex than it seems．
D．People in Darwin's time were more imaginative．
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