问题如下图：
选项：
A. 
B. 
C. 
解释：
are simple interchangeable tools for measuring the returns of fferent asset classes. represent risk of a security markets . Security market inces represent the security markets, market segment, or asset classes. 请问老师C错在哪里？
麻烦老师翻译一下各，怎样才能准确翻译，很多题，在翻译上伤脑筋。
