用来专门在商品包装上标明生产厂家和说明商品名称的标记，包括厂牌、商标等，这种商品包装标记是指（）。

A.等级标记

B.牌号标记

C.唛头

D.一般描述性标记

Which of the following statements is most likely to characterize the principal-agent problem between buyers and sellers of services（）

A. Principals can impose their own objectives on agents.

B. Principals can have complete information about agent behavior.

C. Agents cannot be completely monitored.