There would be no heat or air-conditioning and no toilets in the cargo plane,which was a challenge _____ the trip took n
问题描述：
There would be no heat or air-conditioning and no toilets in the cargo plane,which was a challenge _____ the trip took nearly ten hours.
A.when B.where C.while D.which
答
A
货运飞机上既没有暖气、空调,也没有厕所,当旅程将近十个小时的时候,这真是个挑战.