It is a question that has confused parents for many years：why do children refuse to eat greens？
    Now，two American experts believe they have the answer.
    After studying dozens of babies as they played with different objects，the researchers noted that they were far more unwilling to touch plants than other things.They believe this is because evolution（生物進(jìn)化）has biologically made children be wary of plants.
    Because of susceptibility（敏感性） to illness or injury in the early years of life，the body has designed an inner defence mechanism（內(nèi)部保護(hù)機(jī)制）that limits a child's contact with plants，they think.The researchers believe this is why babies in the study were afraid of touching plants and why children turn their noses up when faced with a plate of broad beans.
    The findings are published in a paper by Dr Annie E Wertz and Dr Karen Wynn，both psychologists at Yale University.
    They wrote， "Throughout human evolution...plants have been important in human's life.Yet，for all of these benefits，plants have always caused very real dangers."
    "Plants produce toxin（毒素）as defences that can be harmful，or even deadly.Some plants also produce physical defences，such as thorns（荊棘）can damage tissues（組織）and cause effects over the whole body."
    They added， "We predicted that babies may have behavioral strategies that reduce dangers caused by plants."
    To test their theory，the researchers studied how children aged eight to 18 months old reacted when presented with a variety of objects.It took much longer for children to grab plants；objects that were pretended to look like plants also caused a slow response time.
    For parents attempting to spoon some peas into the mouth of their child，this finding should come as welcome relief.

（1）What does the underlined word"wary"in the third paragraph mean？

B

B

A．curious
B．a(chǎn)fraid
C．tired
D．certain
（2）What did early humans probably do in order to keep away from illness or injury？

C

C

A．They choose to make more man-made things.
B．They didn't allow their children to touch plants.
C．They chose to have little contact with plants.
D．They tried very hard to escape from the past.
（3）What was plants' role in early human's life？

A

A

A．They were important，in spite of danger.
B．They reacted badly to human evolution.
C．They contributed to the most deaths and illness.
D．They developed human physical defences against dangers.
（4）What's the passage mainly about？

C

C

A．Why some plants are harmful.
B．How humans react to plants.
C．Why children don't like to eat greens.
D．When children form behavioral strategies.