I have ________ French. What about you?

A．many difficulties to learn

B．a few troubles in learning

C．quite a little difficulty to learn

D．a great deal of trouble learning

当前收益率度量的是债券年利息收益占购买价格的百分比，既反映每单位投资能够获得的债券年利息收益，又反映每单位投资的资本损益。（）