城市房屋租赁实行()制度。
A.审批
B.审核
C.登记备案
D.报告
参考答案：C
小亮准备用36元钱买笔和练习本，已知每去笔3.5元，每本练习本1.8元．他买了8本练习本，最多还可以买_________去笔。
—Have you got your exam papers?
—Not yet. I guess they _____ at this moment.
A．are being graded
B．are grading
C．have graded
D．have been graded
