产品价格是由生产成本，（）税金和利润四大要素构成。

A.营销成本

B.固定成本

C.变动成本

D.流通费用

Two mooring lines may be placed on the same bollard and either one cast off first if（）.

A.the eye of the second line is dipped

B.the mooring lines are doubled

C.the bollard has two horns

D.one of the lines is a breast line