Animals can move from place to place, but plants cannot. When an animal is under attack,

　 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 (保护) 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.
【小题1】To defend themselves, oak trees use .A．chemical means B．physical meansC．bitter chemicals D．sandy materials【小题2】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.【小题3】What would be the best title for this passage?A．Plants and AnimalsB．How Plants Defend ThemselvesC．Attacks and DefensesD．How Animals Eat Plant LeavesB

(答案→)B 解析：讲述了植物通过各种方法来保护自己。【小题1】推理题。根据第三段第一行Some plants, such as the oak tree, have thick and hard leaves。可知有厚的坚硬的叶子，这是物理方面的方法。【小题2】细节题。根据倒数第二段第五行This messenger sends to the roots the information to produce more nicotine.【小题3】主旨大意题。通读全文可知文章是关于植物如何保护自己的。

这个问题的回答的对