问题如下：
What will happen in an informationally efficient capital market?
选项：
A.Investors react to all information releases quickly.
B.The price of security reflect all available information fully, quickly and rationally.
C.Active managers can earn positive risk-adjusted returns.
解释：
B is correct.
The price of security fully, quickly and rationally reflect all available information in an informationally efficient capital markets. Because the expected information releases is well reflected in securities' prices, investors can only react to unexpected information releases. If the market is fully efficient, active investment strategies cannot earn positive risk-adjusted returns, and investors should therefore use a passive strategy.
看了有效市场的定义，可是还是不太明白，为什么A不对？
