【题目】I won’t tell the student the answer to the math problem until he on it for more than an hour.
A. has been working B. will have worked
C. will have been working D. had worked
在线课程【答案】A
【解析】
试题分析： 考查动词时态。句意：我直到他已经做这道数学题超过一个小时才告诉这个学生数学答案。根据“for more than an horn。”知选用现在完成进行时态。
考点 : 考查动词时态