I soon found that the work I was doing had already been done by someone else.________, I was

wasting my time. [ ]

A. In other words   

B. In a word

C. First of all  

D. Believe it or not

在系统实施中，应用程序编制的三个层次是( )。

A．分析、设计和编码

B．规划、设计和编码

C．编码、测试和排错

D．设计、编码和测试