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

Given the following information about a firm: Net Sales = $1000 Cost of Goods Sold = $ 600 Operating Expenses = $ 200 Interest Expenses = $ 50 Tax Rate = 34% What are the gross and operating profit margins Gross Operating Margin Operating Profit Margin（）①A. 2O% 15% ②B. 4O% 10% ③C. 40% 20%

A. ①

B. ②

C. ③