Concept:
CPU is the main component of a computer that performs processing tasks.
Step 1: Expand the abbreviation.
\[
{CPU} = {Central Processing Unit}
\]
Step 2: Evaluate options.
(A) \checkmark correct
(B) $\times$ incorrect expansion
(C) $\times$ incorrect
(D) $\times$ incorrect
Hence, the correct answer is Central Processing Unit.