The average age at which people begin to n

问题单项选择题

The average age at which people begin to need eyeglasses vary considerably.

A．varies

B．is varied

C．will vary

D．has been varied

答案

参考答案：A

解析：[分析] 结构应用主句主语为the average age，是单数，应用一般现在时的第三人称单数形式，因此A为答案。