用例之间的三种关系是（）。

A.包含、扩展和简化

B.合取、析取和扩展

C.包含、多态和继承

D.包含、扩展和泛化

An analyst routinely has the opportunity to offer his clients the opportunity to purchase "hot new issues. " He tells his clients that he will distribute each issue equally among those interested, with himself included in the distribution. The clients do not object to this. With respect to Standard Ⅵ (B) , Priority of Transactions, this :（）

A. cannot be a violation because the clients know of the practice and agree.

B. may be a violation because it is impossible to distribute hot new issues equally.

C. may be a violation despite the clients’ approval.