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

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

A. young enoughB. too young toC. 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.

感谢回答，我学习了