In the meeting, the professor expressed his thanks for the aid he from his students.A. re

网友回答

A. received
B. was received
C. have received
(答案→)D. had received
解析：    
试题分析:考查动词时态。根据语境可知获得帮助是发生在动词expressed之前，表示过去的过去，所以用过去完成时，故答案选D。句意：在会议上，教授表达了他对学生们帮助的感激。