Question

       Animals can move from place to place ,but plants cannot. When an animal is under attack ,it can run away or fight back .Plants certainly cannot run away ,and they lack teeth and claws .But plants can defend themselves by using both physical and chemical means.

       Some plants have their own ways to keep animals away .For example ,the leaves of the holly plant have sharp spines（刺）that discourage grass-eating animals .Holly leaves on lower branches have more spines than leaves on upper branches .This is because the lower leaves are easier for most animals to reach.

       Some plants ,such as the oak tree, have thick and hard leaves that are difficult for animals to eat .Some grasses may contain a sandy material ,eating such grasses wears down the animal’s teeth .

       Many plants also have chemical defenses .Some plants produce chemicals that taste bitter or cause an unpleasant reaction. Some plants may fight against an attack by increasing the production of these chemicals .When a caterpillar（毛虫）bites a tobacco leaf ,the leaf produces a chemical messenger .This messenger sends to the roots the information to produce more nicotine .The higher levels of nicotine discourage the caterpillar.

       Many plants depend on both physical and chemical defenses. A certain plant in China ,for instance, has prickly （多刺的）leaves, and each prickle contains poisonous venom（毒液）A single experience with this kind of plant will teach an animal to stay away from it in the future.

68．The holly plant has more spines on the lower leaves because most animals       .

       A．are not tall enough                               B．like the lower leaves only

       C．are not clever enough                           D．can get the lower leaves easily

69．To defend themselves ,oak trees use        .

       A．chemical means                                   B．physical means

       C．bitter chemicals                                   D．sandy materials

70．How does tobacco protect itself against an attack from a caterpillar?

       A．Its leaves fight against the attack by physical means.

       B．Its roots send a messenger to discourage the caterpillar.

       C．Its roots increase the production of nicotine when it is attacked.

       D．Its leaves produce poisonous sand to drive the caterpillar away.

71．What would be the best title for this passage?

       A．Plants and Animals                               B．How Plants Defend Themselves

       C．Attacks and Defenses                           D．How Animals Eat Plant Leaves

Answer 1

68.D 

解析：从文章第二段中的the lower leaves are easier for most animals to reach可以得出正确答案。

69.B 

解析：从第三段中的句子oak tree, have thick ad hard leaves that are difficult for animals to eat，可以得出正确的答案。

70.C 

解析：从第四段可以知道tobacco保护自己不受毛虫的侵害的办法是产生更多的nicotine。

71.B 

解析：因为整篇文章都在讲植物是怎么保护自己的。