Life is like riding a bicycle. ________ your balance, you must keep moving.
#88762
A
Keeping
B
To keep
C
Keep
D
Having kept
推荐题目
As a result of the serious flood, two-thirds of the buildings in the area       .
#90965
A
need to repair
B
needs to repair
C
needs repairing
D
need repairing
The little boy is lucky enough to have escaped ____ to death in the big fire. 
#98699
A
burning
B
to be burned
C
being burned
D
to have been burned