Would you like _____ football?[ ]
A. play
B. to play
C. plays
答案：B
直流电机的磁极铁心是用相互绝缘的硅钢片叠成的，这是为了（）.
A.减小铜损
B.减小铁损
C.防止短路
D.便于加工制造
若x2-2x的值是6，则-3x2+6x+5的值是______．
