Read the following paragraph carefully and choose the best topic sentence from the four possible answers that follow the paragraph by writing A, B, C or D. Researchers divided the 1,400 subjects into two groups. The first group did not stretch before their runs. The second group stretched, having received photographs and specific instructions for a series of simple, traditional poses, like leaning over and touching toes. The volunteers followed their assigned regimens (方法) for three months. About 16 percent of the group that did not stretch were hobbled (跛行) badly enough to miss training for at least three days (the researchers’ definition of a running injury), while about 16 percent of the group that did stretch were laid up (生病) for the same amount of time. The percentages, in other words, were virtually identical. A. Stretching is important before running. B. Running may induce injuries. C. Stretching may not help in preventing injuries in running. D. Identical poses may cause injuries in running. Topic sentence: __________
【正确答案】：C
【题目解析】：本类题型考察的是主题句和推展句之间的关系。主题句是推展句的概括和总结，推展句是主题句的解释和说明。根据这一关系，我们可以通过对推展句的阅读，来确定某个段落的主题句。本段中的推展句通过比较对比的方式得出了一个结论，那就是跑步锻炼时是否进行热身，对身体的伤害并不构成不同的影响。所以，本段的主题句是C。
