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 have no teeth or claws. But plants can protect themselves in both physical and chemical ways.

    Some plants have their own ways to keep animals away. For example, the leaves of the holly(冬青) have sharp prickles(刺) that discourage grass-eating animals. Holly leaves on lower places have more prickles than leaves on upper places. This is because the lower leaves are easier for most animals to reach. Some plants, such as the oak trees(橡树), have thick and hard leaves that are difficult for animals to eat. Some grasses may contain a sandy material, and eating such grasses wears down the animals' teeth. Many plants also have chemical defenses. Some plants produce chemicals that taste bitter(苦) or cause an unpleasant reaction. Some plants may fight against an attack by increasing the production of these chemicals. When a worm bites a tobacco leaf (烟叶), the leaf produces a chemical smell. Many plants depend on both physical and chemical defenses. A certain plant in China, for instance, has prickly leaves, and each prickle has poisonous water(毒液). Only one experience with this kind of plant will teach an animal to stay away from it in the future.

温室大棚是目前进行蔬菜反季节种植的主要技术手段，回答下列问题。

    Crying marriage? Surprising, isn't it? Actually, the custom of crying marriage____ (exist) a long time ago in many areas of Southwest China's Sichuan Province, and remained in fashion until the end of the Qing Dynasty. Though not so popular ____before, the custom is still observed by people in many places, especially Tujia people,____ view it as a necessity of the marriage procedure.

    It is very much the same in different____ (place) of the province. According to elderly people, every bride had to cry at the wedding. Otherwise____ bride's neighbors would look down upon her as a ____(poor) educated girl and she would become the laughingstock of the village. In fact, there were cases in which the bride ____ (beat) by her mother for not crying at the wedding ceremony.

    In a word, crying at the wedding is a way to set off the____ (happy) of the wadding through falsely sorrowful words. However, in the ____ (arrange) marriages of the old days of China9 there were indeed quite a lot of brides who cried over their ____ (disappoint) marriage and even their unhappy life.