根据所给句子的意思，填上合适的单词，并注意其正确形式, 首字母已给出。

小题1:Wang Wei is very stubborn, so it is not easy for her to change her m___________.

小题2:If you have some trouble, you can go to the teacher for a_________.

小题3:Though he is a n________ English speaker, he can’t speak English very fluently.

小题4:I don’t think it was an accident at all. Your brother did it on p____________.

小题5:I was very excited. It took me some time to c______ down myself.

消极债券投资策略包括( )。

A．久期免疫策略

B．收益曲线骑乘策略

C．子弹型策略

D．指数化投资策略