The scientists ________ on the new medicine for two years. They will succeed in no time. 
#38384
A
work
B
are working
C
have worked
D
will work
推荐题目
So far, we           3000 English words.
#40151
A
learned
B
have learned
C
studied
D
learn
The radio says it _____ later in the day, then we can go out to play.
#41994
A
stops to rain
B
stops raining
C
will stop raining
D
will stop to rain
We____here two hours ago . So we___ _here for two hours .
#39938
A
have arrived , have been
B
have come , have been
C
came , have come
D
arrived , have been