Are the parents who let their child who is walk in the dark alone at night considerate?A.

问题补充：

Are the parents who let their child who is walk in the dark alone at night considerate?

A. young enough

B. too young to

C. not old enough to

D. so young

答案：

A. young enough

B. too young to

C. not old enough to

(答案→)D. so young

解析：分析句子结构，who is so young 在句为修饰的定语,另有let sb.do sth.