用适当的数词完成句子。

1. There are _____ months in a year.

2. Bill is nine years old. I'm four years older than (比……大) him. So I'm _____ years old.

3. Ten and eleven is _____.

4. April has _____ days.

5. In this class there are _____ students, nineteen boys and twenty-five girls.

皇帝和大臣讨论如何选拔人才。大臣主张应该只问他们个人能力的高低，不要计较他们的家世背景。皇帝反对大臣的说法，强调历时久长的世家才是培养人才的沃土，这件事最可能发生在哪一时期（）

A.秦汉

B.魏晋南北朝

C.宋元

D.明清