Putting out forest fire is regarded as one of _____ problems in the world.( )
A. |
difficult |
B. |
more difficult |
C. |
most difficult |
D. |
the most difficult |
Putting out forest fire is regarded as one of _____ problems in the world.( )
A. |
difficult |
B. |
more difficult |
C. |
most difficult |
D. |
the most difficult |