如果a÷b=4，那么a和b成______比例关系．
因为a÷b=4，
即a与b的比值一定，符合正比例的意义，
所以a和b成正比例，
故答案为：正．
Mary three of her classmates invited to the party. [ ]
A. as well; has been
B. and; have
C. as well as；was
D. as good as; were
招标代理机构从事招标代理业务所必须遵循的原则是( )。
A．公平
B．公开
C．公正
D．守法
E．诚信
