权证交易实行价格涨跌幅限制，下列计算涨跌幅价格的公式正确的有( )。

A．权证涨幅价格=权证前一日收盘价格+(标的证券当日涨幅价格-标的证券前一日收盘价)×125%×行权比例

B．权证涨幅价格=权证前一日收盘价格+(标的证券当日涨幅价格-标的证券前一日收盘价)×25%×行权比例

C．权证跌幅价格=权证前一日收盘价格-(标的证券前-日收盘价-标的证券当日跌幅价格)×125%×行权比例

D．权证跌幅价格=权证前一日收盘价格-(标的证券前-日收盘价-标的证券当日跌幅价格)×25%×行权比例

An investor's portfolio has a mean return of 15 percent and a coefficient of variation of 1.8. If the risk-free rate of return is 5 percent, the portfolio has the sharpe ratio is closet to:（）

A. 0.27.

B. 0.37.

C. 0.56.