Some scientists have questioned the theory ______ CO2 is causing dangerous global warming.
#68429
A
which
B
what
C
that
D
why
推荐题目
Make marks _______ you have questions. 
#66894
A
which
B
in which
C
where
D
in where
   ______they have been working hard to find?
#70400
A
Is that what
B
Is that
C
It is that
D
Is it that