(74) systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and (75) on the disk, and controlling peripheral devices such as disk drives and printers.

A．Operation

B．Operator

C．Operating

D．Operate

民航空管安全管理体系应当做到有计划、有落实、有检查、有跟踪的闭环管理。