某次作文竞赛设优胜奖和新人奖。已知：（1）新兴小学和红梅小学两校获奖的人数比为6：5。（2）新兴小学、红梅小学两校获新人奖的人数总和占两校获奖人数总和的60%。（3）新兴小学、红梅小学两校获新人奖的人数之比为5：6。问新兴小学校获新人奖的人数占该校获奖总人数的比重是多少（）
A．20%
B．30%
C．50%
D．60%
参考答案：C
解析：
已知新兴小学、红梅小学两校获新人奖的人数之比为5:6，那么设新兴小学获新人奖的人数为5份，红梅小学为6份。因为新人奖的人数占两校获奖人数总和的60%，那么新兴小学获新人奖的人数占获奖总人数的
。又因为新兴小学、红梅小学两学校获奖的人数比为6:5，所以设总人数为11份，新兴小学得奖的人数占其中6份。可知新兴小学获新人奖者占该校获奖总人数的比重为
。
| About fifty years ago, plant physiologists set out to grow roots by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and the usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along fine on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require energy, of course. The process of respiration uses sugar to make the high energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen. The study of isolated roots has provided an understanding of the relationship between shoots and roots in intact plants. The leaves of the shoots provide the roots with sugar and vitamins, and the roots provide the shoots with water and minerals. In addition, roots can provide the shoots with organic nitrogen compounds. This comes in handy for the growth of buds in the early spring when leaves are not yet functioning. Once leaves begin photosynthesizing, they produce protein, but only mature leaves can "export" protein to the rest of the plant in the form of amino acids. |
Which of the following best describes the organization of the passage
A．The results of two experiments are compared.
B．A generalization is made, and several examples of it are given.
C．The findings of an experiment are explained.
D．A hypothesis is presented, and several means of proving it are suggested.