It is the first time I ____ to visit the Great Wall. 
#92611
A
came
B
come
C
have come
D
had come
推荐题目
 It never _____  humans until the mid­1990s that some animals can be cloned.
#92718
A
occur
B
is occurred
C
occurred to
D
occurred
Never before ________ buying a computer, but now it seems a necessity in my everyday life.
#93867
A
did I think of
B
have I thought of
C
I thought of
D
I have thought of
A new study suggests that the more teenagers watch television,_______ develop depression(抑郁症) as young adults.
#92109
A
the more likely they are to
B
the more likely they are
C
they are the more likely to
D
the more likely are they