如果投资者购买债券并持有到期，衡量他的收益状况的指标是：

A．当期收益率

B．持有期收益率

C．到期收益率

D．赎回收益率

A man was sighted as he fell overboard. After completing a Williamson turn，the man is not sighted. What type of search should be conducted?（）

A.Expanding circle

B.Sector search

C.Parallel track pattern

D.Datum-drift search