外加剂的掺量（按固体计算），应以水泥重量的百分率表示，称量误差不应超过规定计量的（）%。
A.1.5
B.2.0
C.2.5
D.3.0
参考答案：B
(2013·成都一模)________ all the homework assigned by the school, the students have to work at it till midnight.
A．Completing
B．To complete
C．Having completed
D．To have completed
老舍小说独特的贡献是什么？
