—What’s your impression of the Great Wall?—Wonderful! Once       , it can never be forgotten.
#96766
A
seen
B
seeing
C
being seen
D
saw
推荐题目
__________of danger in the street at night, she had to go home, with a friend_________ her. 
#94580
A
Warned, followed
B
Warning, following
C
Having warned, following
D
Having been warned, following
---What do you think of his talk on Information Technology? ---Oh, excellent. It's worth ________.
#89657
A
listening to
B
being listened to
C
listening of
D
to be listened to