一个正方形的边长是3米，它的周长是______．长方形的长是8厘米，宽是5厘米，

引入期的定价策略有（）。

A.维持价格策略

B.驱逐价格策略

C.撇脂定价策略

D.渗透定价策略

E.满意定价策略

It was announced that only when the fire was under control ___ to return to their homes. [ ]

A. the residents would be permitted    

B. had the residents been permitted

C. would be residents be permitted      

D. the residents had been permitted

29．---- I wonder how much you charge for your services.

---- The first two are free ____  the third costs $30.

A．while

B．until　　

C．when

D．Before

孙中山先生诞生于哪一天。

装置自聚物的生成与（）有关。

A.氧含量

B.焦油含量

C.TBC含量

D.甲苯