练习说明
句子填空 题目要求：阅读文段，从文中挑选原词补全句子，每道题目都有特定的字数要求，以黑体加粗字标示。请把答案填到每题空缺处。
Choose ONE WORD ONLY from the passage for each answer.
第 1 题
To test his theory, Tewksbury grew plants that produced hot, spicy chilies as well as plants that yielded mild chilies (though both were from the same species). When he offered the fruits of those plants to laboratory rats and mice, they ate the mild chilies but avoided the ones with a strong concentration of capsaicin. He later found that birds do not seem to mind eating even the hottest chilies and, in fact, that the capsaicin had the strange effect of retarding birds' digestion, which helps some seeds germinate, possibly by softening the seed coat.
Rodents avoided chilies with a high ______________ of capsaicin.
第 2 题
Even so, Tewksbury didn't believe that deterring rodents and slowing bird digestion were enough to explain why the spicy heat of chilies evolved. Instead, he thinks that a chili's heat protects it from disease that a certain fungus can trigger, the primary reason chili seeds die prior to being dispersed. In looking at chili populations that contain both hot, spicy, and mild plants, Tewksbury has found that the more capsaicin, the less fungal infection. '
Another role of capsaicin is in reducing infection caused by a ________.
第 3 题
Capsaicin demonstrates the incredible elegance of evolution,' says Tewksbury. The capsaicin discourages rodents and deters microbes - and humans harness this ability when they use chilies to preserve food- but capsaicin doesn't prevent birds from eating chili fruit and spreading seeds. 'Once in a while, the complex, often conflicting demands that nature places on complex traits result in a truly elegant solution. This is one of those times.'
Tewksbury considers the role of capsaicin in chilies to be an example in nature of the beauty of _______________.
第 4 题
The machines grew more refined and the idea spread, By the 1930s, Adolph Levitt's machines were earning him $25 million a year, mostly from deliveries all over the US. One article noted that the doughnut machine had diminished the prejudice that had been directed at the ‘grease-soaked product' by making it into a light, puffy product of a machine.’
Levitt’s doughnut machines earned $25 million a year and helped reduce ____ surrounding the doughnut.
第 5 题
By the 1934 World’s Fair in Chicago, doughnuts were billed as “the food hit of the Century of Progress." A doughnut cost less than five cents, within reach of the era's countless poor. Occasionally, the treats were served with messages to lift the spirits: ‘As you go through life make this your goal: Watch the doughnut, not the hole.’
sometimes doughnuts had _______________ that were meant to cheer people up.
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