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
网友回答
(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。