Which of the following is true

A．Alex will help you in a half hour, with your English.

B．English takes about half my spare time.

C．Studying English one half hour per day is good.

D．Half the paper was in English.

某商业银行签订买入500万美元的即期合约，同时又签订一年后卖出500万美元的远期合约，该银行使用的是( )交易方式。

A．货币互换
B．期限互换
C．利率互换
D．期权互换