In a perfectly efficient market, portfolio managers should do all of the following EXCEPT:（）

A. rebalance their portfolio when changes are necessary.

B. diversify to eliminate systematic risk.

C. quantify their risk and return needs within the bounds of the client’s liquidity, income, time horizon, legal, and regulatory constraints.

公文生效的标识是（）。

A.公文开始执行

B.公文复核结束

C.主送机关收到公文

D.发文机关盖章或签发人署名