____some doubt among scientists about the cause of cancer.
#92930
A
It exists
B
There exists
C
There is existing
D
It is existing
推荐题目
If city noise _______ from increasing, people _______ shout to be heard even at the dinner table 20 years from now.
#94723
A
are not kept; will have to
B
are not kept; have to
C
do not kept; will have to
D
do not kept; have to
It was not until the beginning of the twentieth century________to explore space.
#93086
A
did man begin
B
when man began
C
that man began
D
then man began
You’re＿＿＿＿＿your time trying to persuade him. He’ll never join us.
#94945
A
spending
B
wasting
C
losing
D
missing
It’s the first time that he has been to Australia ,______?
#94116
A
isn’t he
B
has’t he
C
isn’t it
D
hasn’t it