粗糙的大五金商品的除锈可以用（）。
A.钢丝刷除锈
B.砂布除锈
C.纱布蘸去污粉除锈
D.纱布蘸煤油洗擦
参考答案：A
有理数a、b、c满足条件2ab＞c2和2ac＞b2，则①a2+b2＞c2；②a2﹣b2＞c2；③a2+c2＞b2④a2﹣c2＞b2中，正确不等式的序号是（ ）和（ ）．
This book _____ Tom's father's, because his name is on the book. [ ]
A. maybe
B. may be
C. must be
D. must
