In the USA, _______ Thanksgiving Day is a harvest festival. Traditionally, it is _______ time to give thanks for the harvest and express gratitude in general.

A．the; a

B．/; the

C．/; a

D．the; the

在数据流图中，

(椭圆)代表______。

A．源点

B．终点

C．加工

D．模块