一个育龄妇女婚前检查，风疹IgG抗体阴性。婚后育龄妇女准备要小孩，但当地每年都有风疹散在流行。为防止先天性风疹综合征发生的最好办法是（）

A.该育龄妇女不接触出疹的病人

B.保持家中空气流通和空气消毒

C.注射风疹减毒活疫苗，并在3～6个月后再怀孕

D.注射丙种球蛋白和胎盘球蛋白

E.推迟1年怀孕

(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