Not until World War II ______ to use new chemical techniques to purify penicillin.
#81196
A
they managed
B
that they managed
C
did they manage
D
they didn’t manage
推荐题目
By the side of the teaching building of our school _____, which was completed in 2009. 
#82862
A
there standing the library
B
does the library stand
C
the library stands
D
stands the library