单项选择题
A. 统计数字表明，按平均数计算，母亲受教育年限越长，她的家庭人口就越少。 B. 统计数字表明，家庭平均人口的增长与母亲受教育的年限成反比。 C. 统计数字表明，母亲受教育的时间越长，她的家庭就越大。 D. 统计数字表明，母亲受教育的水平随着她的家庭人口的增多而增高。
A. They had to stand under the pressure three times the force of gravity. B. Ten days later in the test, they had to spend other twenty days in bed. C. During the whole test, they suffered backaches and other discomforts. D. Some of the women suffered great loss of calcium.
A. People who want to take their own lives often disguise their feelings. B. It is difficult to describe what kind of people tend to commit suicide. C. Suicide has been a problem in most cities since ancient times. D. People who commit suicide all share certain characteristics.