较易推广的氟防龋措施是（）
A.含氟牙膏
B.氟饮水
C.氟盐
D.氟片
E.氟滴剂
参考答案：B
It was because of the bad weather __________ the football match had to be put off.(推迟)
A．so
B．so that
C．why
D．that
润滑油按其使用范围可分为哪几种？
