这题不理解，我觉得a和c好像都对了

问题如下：

If securities markets are semi-strong-form efficient, the most appropriate role of a portfolio manager is to:

选项：

A.

invest by analyzing publicly available information to consistently generate abnormal returns.

B.

manage portfolios with appropriate diversification and asset allocation, taking into consideration investor preferences

C.

exploit appropriate trading rules and serial correlations for achieving excess returns.

解释：

If markets are semi-strong-form efficient (which also encompasses weak-form efficiency), the role of a portfolio manager is not necessarily to beat the market, but rather to establish and manage a portfolio consistent with the portfolio’s objectives, with appropriate diversification and asset allocation, while taking into consideration the risk preferences and tax situation of the investor.