单选题 (21) put computers to practical business use, but below the surface it is the heart of an (22) - the kernel - that provides the technical wizardry to juggle multiple programs, connect to networks and store (23) .
A traditional kernel provides all the functions for applications. The kernel (24) memory, I/O devices and parcels out processor time.
The kernel also supports (25) and fault tolerance, which is the ability to recover automatically when parts of the system fail.

【正确答案】 C

【答案解析】[解析] 应用程序(Applications)使计算机有了实际的商业用途，但在这种表面现象之下(operating system)，是操作系统(operating system)的内核为多程序间的切换、网络的连接和数据(data)存储提供了技术的支持。传统的内核为应用程序提供各种功能，内核管理(manage)内存、I/O设备并分配CPU的时隙。内核还支持安全机制(security)及容错机制，即当系统的一部分崩溃时，内核能够自动恢复。