问题如下：
Assume the expected return on all stocks in the market represented by point W , and the expected return on all bonds in the market represented by point Y on the graph.
The efficient frontier consists of the portfolios between and including:
选项：
A.Y and W.
B.Y and X.
C.X and W.
D.none of the above.
解释：
C is correct.
考点：有效前沿
解析： 有效前沿始于全球最小方差投资组合，向右上延伸，包括对任何给定风险水平（标准差或方差）具有最大预期收益的投资组合。
这题我在新版本里面是看不到图的，但是因为旧版本的时候做过了所以知道图大概的样子，可以的话麻烦修复一下bug吧，谢谢啦。
