The（）has several major components, including the system kernel,a memory management system, the file system manager, device drivers, and the system libraries.

A．application

B．information system

C．network

D．operating system

脑膜炎奈瑟菌的唯一宿主是

A．人
B．猫
C．狗
D．黑猩猩
E．豚鼠