若3x=7y，那么x和y成______比例．
因为3x=7y，所以xy=73（一定），是x、y的比值一定，所以x、y成正比例．
故答案为：正．
---- Your daughter has won the first prize in the contest .What a smart girl she is !
--- .______________ .
A It’s nice of you to say so B .She was really lucky
C . No one else could do it D . Oh ,not really
国家对哪些企业实行安全生产许可证制度？
