A．pplications put computers to practical business(67), but below the(68)it's the heart of an operating system-the kernel-that provides the technical wizardry to juggle multiple program, connect to networks and store(69).

A． traditional kernel provides all the functions for applications. The kernel(70)memory, I/0 devices and parcels out processor time.

The kernel also supports security and fault(71), which is the ability to recover automatically when parts of the system fail.

A．used

B．use

C．apply

D．applied