单项选择题

在系统中定义并获取通知服务的代码使哪一个?()

A.NotificationManager manager =(NotificationManager)getService(NOTIFICATION_SERVICE)
B.NotificationManager manager =(NotificationManager)getService(NOTIFICATION_SERVICE_Manager)
C.NotificationManager manager =(NotificationManager)getSystemService(NOTIFICATION_SERVICE_Manager)
D.NotificationManager manager =(NotificationManager)getSystemService(NOTIFICATION_SERVICE)