---Sorry, Professor Smith. I didn't finish the assignment yesterday.

---Oh, you      have done it as yesterday was the deadline.

A．must

B．mustn't

C．should

D．shouldn't

以下叙述中正确的是( )。

A．程序设计的任务就是编写程序代码并上机调试
B．程序设计的任务就是确定所用数据结构
C．程序设计的任务就是确定所用算法
D．以上三种说法都不完整