Mr. Richard was disappointed that many students who had signed up for his adventure course at the last moment.
A. left out
B. got out
C. passed out
D. dropped out
网友回答
A. left out
B. got out
C. passed out
(答案→)D. dropped out
解析：考察词组辨析。Leave out 遗漏，省去 get out 离开 pass out 昏倒，失去知觉 drop out 退出，退学
句意为，理查德先生非常失望，因为很多报名参加他的冒险课程的人在最后一刻选择了退出。