Somebody who is very risk averse could say, I want to hold only the riskless assets because I just don't like any risk at all.

有些极度惧怕风险的人可能会说，我只想持有那些没有风险的资产,因为我压根就不想跟风险打交道。

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Tangent means that it has the same slope, it just touches the efficient portfolio frontier for risky assets at one point, and the slope of the efficient portfolio frontier, including the riskless asset, is a straight line that goes through the tangency point, here.

相切意味着斜率相同，它与包含风险资产的有效边界,交与一点，而包含无风险资产的，有效边界，则是一条过切点的直线，切点在这里。

耶鲁公开课 - 金融市场课程节选