—Three problems are too hard to _____. Will you give me some advice?

—There are many ways. The most important is to have a careful plan.  [ ]

A. work out

B. look out

C. hand out

D. break out

股票期货是以( )为标的物的期货合约。

A．一组股票价格指数

B．某只股票的收益率

C．单只股票价格

D．整个市场的股票加权价格