The surplus value that results when a particular resource or product is fixed in supply and market price is higher than what is required to bring the resource or product onto the market and sustain its use can be defined as:（）

A. normal profit.

B. economic rent.

C. consumer surplus.

西方式插花的四面观花型有（）

A.半球形

B.球形

C.塔形

D.圆形

E.水平形