Professor Smith, along with his assistants, ________ on the project day and night to meet the deadline.

A．work

B．working

C．are working

D．is working

承租人未经出租人同意，对租赁物进行改善或者增设他物的，出租人可以要求承租人( )。

A．恢复原状

B．赔偿损失

C．赔礼道歉

D．解除合同