把一根火柴梗平放在蜡烛火焰中，约1s 后取出，可观察到火柴梗    [ ]

A．均匀地被烧黑    

B．放置在外焰部分被烧黑最重    

C．放置在内焰部分被烧黑最重    

D．放置在焰心部分被烧黑最重

With respect to determining the optimal portfolio for an investor, which of the following statements is most accurate（）

A. Two investors may choose the same optimal portfolio even if their indifferent curve are different.

B. Less risk-averse investors will have steeper utility curves than more riskaverse investors.

C. The optimal portfolio lies at the point of tangency between the efficient frontier and indifference curve with the highest possible utility.