The boy asked his father .
A. where it happens
B. when did it happen
C. what did it happen
D. how it happened
网友回答
A. where it happens
B. when did it happen
C. what did it happen
(答案→)D. how it happened
解析：根据句子的结构可知本句是一个宾语从句。根据的宾语从句的时态规则“如果主句是过去时，则从句应该用过去时的某种时态。”可知，主句用的过去时，则从句应该使用过去时，所以应该排除A；又根据宾语从句的语序要用陈述句语序可知，应该将BC排除。所以本题选D。