飞行中执行内八字或者外八字掰杆操作，飞行器将（）。
A.电机停转，坠落
B.自动降落
C.原地悬停
D.返航
参考答案：A
— Did you see Mr. Chen yesterday afternoon?
— No. When I got to school, he ______ already. [ ]
A. left
B. has left
C. had left
D. was leaving
急性结膜炎（俗称红眼病）的临床表现有（）
A.眼部瘙痒不适
B.结膜充血水肿
C.视力减退
D.分泌物增多
E.屈光不正
