Tom sat under a tree chatting with his friends and his teacher, stood up in no time.
A. seeing
B. seen
C. saw
D. to see
网友回答
(答案→)A. seeing
B. seen
C. saw
D. to see
解析：in no time“立刻，马上”； his teacher空白处填非谓语形式，作时间状语；逻辑主语是Tom，Tom和see是主谓关系，故用主动形式seeing。“（Tom）看到老师时，立刻站了起来。”故选A。