Li Yundi began to learn the piano _____ the age of four and took part _____ the 14th Chopin International

Piano Competition in 2000.[ ]

A. in; at

B. in; in

C. at; in

D. at; on

小企业长期债券投资在持有期间发生的应收利息应当确认为（）。

A.投资收益

B.管理费用

C.主营业务收入

D.其他业务收入