问题如下：
What's the main objective for investors to construct a portfolio?
选项：
A.Investors want to reduce the risk.
B.Investors try to avoid investment disasters.
C.Investors plans to provide downside protection of assets.
解释：
A is correct.
The composition of a portfolio mainly provides diversification. This helps the investor to reduce the risk or the overall volatility. Porfolio cannot guarantee to provide downside protection or avoid make any losses.
a不对吧，构建portfolio是最大化value，而不是最小化risk吧
