There’s no way of knowing why one man makes an important discovery         another man, also intelligent, fails.
#39533
A
since
B
If
C
as
D
while
推荐题目
— _______  do you use the Internet ?    —Twice a week. 
#42470
A
How often
B
How soon
C
How long
D
How Many times
I have no brother, but Jim has.
#43794
A
doesn’t have
B
am not
C
am not have
D
don’t have