The road is covered with snow. I can't understand ________ they insist on going by motorbike.
A.whyB.whetherC.whenD.how在线课程A
思路分析：本题考查宾语从句的用法。根据前面“路为雪覆盖”和后面“他们骑摩托车”得知，此处应当选择why，表示我不解的原因。句意：路上都是雪。我不明白他们为什么坚持要骑摩托车去。