Explanation:

A kilobyte (KB) is a standard unit of digital information storage. In computing, memory units are typically based on powers of $2$. One kilobyte is precisely $2^{10}$ bytes, which calculates to $1024$ bytes. Option (b) correctly states $1024$ bytes. Option (a) $612$ bytes, (c) $2048$ bytes ($2 \text{ KB}$), (d) $4096$ bytes ($4 \text{ KB}$), and (e) $8192$ bytes ($8 \text{ KB}$) are incorrect as they do not represent the standard definition of a kilobyte. The binary nature of computer memory means that powers of $2$ are used for these fundamental units, unlike the decimal prefixes used in other scientific contexts.