从下面提供的答案中选出入下列英文语句中______内的正确答案。 Applications put computers to practical business (1) , but below the (2) it's the heart of an operating system-the kernel-that provides the technical wizardry to juggle multiple program,connect to networks and store (3) ． A traditional kernel provides all the functions for applications.The kemel (4) memory, I/O devices and parcels out processor time. The kernel also supports securityand fault (5) , which is the ability to recover automatically when parts of the system fail.