语法填空 Animals can move from place to place, 1 plants cannot．When an animal 2 unde

语法填空

Animals can move from place to place, 1________ plants cannot．When an animal 2________ under attack, it can run away or fight back．Plants certainly cannot run away, and they lack teeth and claws．But plants can defend 3 ________ by using both physical and chemical means．

Some plants have their own 4________ 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 5________ leaves on upper branches．This is 6________ the lower leaves are easier for most animals to reach．

Some plants, 7________ as the oak tree, have thick and hard leaves that are difficult for animals to eat．8________ grasses may contain a sandy material; eating such grasses wears down the animal’s teeth．

Many plants also 9________ chemical defenses．Some plants produce chemicals that taste bitter or cause an unpleasant reaction．Some plants may fight 10________ an attack by increasing the production of these chemicals．

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