B的idiosyncratic是什么意思啊

问题如下：

If the return on asset classes can be described as a function, which is the most accurate description?

选项：

It describes the failure of arbitrage.

It describes the exposure to the idiosyncratic risks of those asset classes.

It describes the exposure to sets of systematic factors relevant to those asset classes.

解释：

C is correct.

Returns on asset classes primarily reflect exposures to certain sets of the systematic risks of the asset classes.