合同也可以是无偿合同。( )
参考答案：对
解析： 合同可以是有偿合同也可以是无偿合同。
---________ he still _________ in his office?
---No. He __________ back home.
A．Is; working; went
B．Has; worked; is going
C．Is; working; has gone
D．Did; work; is going
