According to the rule，used batteries _______ be dropped in the red bin for harmful wastes．（ ）
| A． |
must |
B． |
need |
C． |
can |
D． |
may |
It's necessary for students ______with their teachers．（ ）
A．communicateB．communicating
C．to communicate
It's time for I'm a Singer，please ______ the TV．（ ）
A．turn onB．turn offC．open
Yu Gong kept moving the mountains，______ he was very old．（ ）
A．soB．althoughC．but
We ______ the tea set for three years．（ ）
A．have hadB．hadC．have been
The sweater ______ belong to Jim．It's much too large for him．（ ）
A．mustn'tB．can'tC．needn't