By the time students complete that course they know two computer languages and have no trouble （）their own programs.

单项选择题Our principal insists that all students （）every school rule regarding dress and smoking.

A．will follow
B．should follow
C．must follow
D．need follow

单项选择题If I （）a little harder, a little longer and a little more creatively, our business （）perfectly.

A．worked……would have run
B．had worked……would have run
C．had worked……would run
D．work……would run