单选题：Operating systems provide certain levels of interfaces. However,

Operating systems provide certain levels of interfaces. However, _____ is in general not provided by OS. @[A](1)
A. Application programming interface (API)
B. Command line interpreter
C. Graphic user interface (GUI)
D. System call





A.Application programming interface (API)
B.Command line interpreter
C.Graphic user interface (GUI)
D.System call


答案：A