A number of birdwatchers in Zhalong Nature Reserve. The number of them500.A. are areB. is

问题补充：

A number of birdwatchers in Zhalong Nature Reserve. The number of them500.

A. are, are

B. is, is

C. is, are

D. are, is

答案：

A. are, are

B. is, is

C. is, are

(答案→)D. are, is

解析：句意：许多观鸟者在扎龙自然保护区。他们的数量是500。A number of 许多，修饰复数名词，含有A number of 的短语作主语，谓语动词使用复数形式；The number of···的数量，用作主语时，谓语动词使用第三人称单数形式。所以选D。