--Have you heard of that? Tom recently bought a new car and an expensive flat.

--________? He even couldn’t have enough money to pay for the rent.

A．How about

B．Why not

C．How come

D．So what

数据流图用于抽象描述一个软件的逻辑模型，数据流图由一些特定的图符构成。下列图符名标识的图符不属于数据流图合法图符的是______。

A．控制流

B．加工

C．数据存储

D．源和潭