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

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.
【小题1】The holly plant has more spines on the lower leaves because most animals .A．are not tall enough B．like the lower leaves onlyC．are not clever enough D．can get the lower leaves easily【小题2】To defend themselves, oak trees use .A．chemical means B．physical meansC．bitter chemicals D．sandy materials【小题3】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4】What would be the best title for this passage?A．Plants and Animals B．How Plants Defend ThemselvesC．Attacks and Defenses D．How Animals Eat Plant LeavesD

(答案→)D 解析：本文主要讲述的是不能移动的植物是如何保护自己的，有些植物采取了物理学上的方法，有些采取了化学上的方法，让自己免受有关动物的伤害，保护自己。【小题1】D 细节题。根据文章第二段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.说明D正确。【小题2】B 细节题。根据第三段Some plants, such as the oak tree, have thick and hard leaves that are difficult for animals to eat.说明oak tree使用的是物理上的方法，让个树叶更硬跟难吃。而有些植物使用的是化学物质。故B正确。【小题3】C 细节题。根据第四段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.说明树根发出指令分泌出更多的nicotine，故C正确。【小题4】B 主旨大意题。本文主要讲述的是不能移动的植物是如何保护自己的，有些植物采取了物理学上的方法，有些采取了化学上的方法，让自己免受有关动物的伤害，保护自己。故B正确。

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