3．The level of the cuddle chemical in humans will not increase when ________．

　　A．they talk to a wolf

　　B．they play with a dog

　　C．they hug newborn babies

　　D．they look into a dog's eyes

　　A　[细节理解题。根据文章最后一句可知，人类和狼之间的互动交流不会使人体内的"拥抱荷尔蒙"增加。]

　　4．The passage is probably taken from ________．

　　A．a story book B．a science magazine

　　C．science fiction D．a text book

　　B　[文章出处题。根据文章内容可知本文主要是讲一个科学研究的，由此可推断本文最有可能摘自一本科学杂志。]

　　B

　　Many gardeners believe that "talking" to their plants helps them grow-it turns out that they may not be crazy after all.According to the scientists from the University of Exeter, plants may keep communicating with each other through a secret "unseen" language.

　　For their experiment, the scientists picked a cabbage plant that is known to send out a gas when its surface is cut.In order to get video evidence of the communication, they changed the cabbage gene by adding the luciferase(荧光素酶), which is what makes fireflies(萤火虫)glow in the dark.

　　When the changed cabbage plant was in full bloom, they cut a leaf off with a pair of scissors, and almost immediately, thanks to the luciferase, they could see the plant sending out "methyl jasmonate(茉莉酸甲酯)"．

　　While this was a known fact, what was surprising was the fact that the minute this gas began to give out, the nearby cabbage plants seemed to sense some kind of danger and started to send out a gas that they normally have to keep enemies like caterpillars(毛虫)away.

What the scientists are not sure is whether the plants are trying to warn the other leaves or the near plants about the danger-something that will require further