-This problem is very difficult.       -I know,but Jack has           working it out. 
#38799
A
succeed in
B
succeeds in
C
succeeding in
D
succeeded in
推荐题目
I began watching here an hour ago, but now nothing _______ yet.
#36538
A
happens
B
will happen
C
happened
D
has happened
Listen! The phone ___. Please go to answer it.
#42252
A
rings
B
is ringing
C
rang
D
will ring
I believe my dream  _________ true in the future .
#40260
A
comes
B
came
C
Will come
D
To come