The correct answer is: C. backs up the computer.
Backing storage is a secondary storage device that stores data permanently. It is used to back up the computer’s main memory, which is a volatile storage device that loses its data when the power is turned off. Backing storage is also used to store data that is not currently being used by the computer, such as files, programs, and operating system files.
The other options are incorrect. Option A is incorrect because backing storage is not always kept at the back of the CPU. Option B is incorrect because backing storage is not slow and backward. Option D is incorrect because backing storage does not lag behind the main memory.
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