题目

Mike used to be a top student, but he______ behind since he lost himself in computer games.A. fell B. has fallenC. was D. has been 答案：【答案】D【解析】试题分析：句意：迈克过去是一名尖子生。但是自从他沉迷于电脑游戏后，他落后了。根据since可知本题应该用现在完成时，fall behind落后，是个瞬间动作，当句中有since, for等表示时间段的时间状语时，要把瞬间动作改为持续动作，所以应该用be behind，故选D。The company offered a number of chances for teachers’ professional________. (develop)