He is to go to school now.A. young enoughB. enough youngC. enough oldD. old enough

问题补充：

He is to go to school now.

A. young enough

B. enough young

C. enough old

D. old enough

答案：

A. young enough

B. enough young

C. enough old

(答案→)D. old enough

解析：句意：他现在年龄足够大了能够去上学了。enough作为副词，修饰形容词或是副词时，放在形容词副词的后面，根据句意，故选D.