number of children born to a woman in her lifetime

例句：

1. 1. The number of studentsin the class is 30.
   班上的学生有30个。
2. 2. Thenumber of books on theshelf is increasing.
   书架上的书的数量正在增加。
3. 3. The number of peoplewho have signed up for the event hasdoubled.
   报名参加该活动的人数翻了一番。