The workers have to ___rubbish to keep the mountains clean.( )
A. |
stand up |
B. |
pick up |
C. |
mix up |
D. |
give up |
The workers have to ___rubbish to keep the mountains clean.( )
A. |
stand up |
B. |
pick up |
C. |
mix up |
D. |
give up |