He is too old to run to catch up with the young boy.A. fast enoughB. fastly enoughC. enoug

问题补充：

He is too old to run to catch up with the young boy.

A. fast enough

B. fastly enough

C. enough fast

D. enough quickly

答案：

(答案→)A. fast enough

B. fastly enough

C. enough fast

D. enough quickly

解析：考查enough的用法。句意“他太老了以至于不能赶上那个小男孩。”enough修饰形容词、副词时要后置；排除C、D；fast是副词，排除B。故选A。