【正确答案】 C

【答案解析】[解析] 期末考试前所有学生都忙着复习。句中prior to：在…之前。during：在…期间，如：The thief broke into the house during the night．小偷在夜间破门进入住宅。after：在…之后，如：After graduation he went abroad．毕业后他去了国外。before：在…之前，如：B comes before C in the alphabet．B在字母表里排在C之前。for：因为，如：We must start early, for it will take two hours to drive to the airport．我们得早点动身，因为开车去机场得花两个小时。只有before意思上和prior to最接近。