在确定写字楼租金时，最低租金水平应是能够抵偿抵押贷款还本付息、()和空置损失的租金

A、建造费用 

B、人工费用 

C、经营费用 

D、广告费用

We make it a rule that each of us _________ the bedroom one day a week.[ ]

A. has cleaned    

B. have cleaned    

C. cleans        

D. clean