With the help of high technology, more and more substances _________ in the past years.
#101033
A
discovered
B
have discovered
C
had been discovered
D
have been discovered
推荐题目
Wherever I ____these days. I always carry my umbrella.
#104189
A
am going
B
shall go
C
go
D
should go
I arrived late; I _____ the road to be so iey. 
#104993
A
wouldn’t expect
B
haven’t expected
C
hadn’t expected
D
wasn’t expecting