--- Is this the first time you ___ Xiamen?

--- No. But the first time I ____ here, the city wasn’t so beautiful.

A．visited, come

B．visited, have come

C．have visited, came

D．have visted, have come

控制器的功能是( )。

A．指挥、协调计算机各部件工作

B．进行算术运算和逻辑运算

C．存储数据和程序

D．控制数据的输入和输出