B哪里错了

问题如下：

With respect to rational and irrational investment decisions, the efficient market hypothesis requires:

选项：

A.

only that the market is rational

B.

that all investors make rational decisions

C.

that some investors make irrational decisions

解释：

The efficient market hypothesis and asset-pricing models only require that the market is rational. Behavioral finance is used to explain some of the market anomalies as irrational decisions.