What is the unit symbol for kilobyte?

The correct unit symbol for kilobyte is "kB." This notation uses a lowercase "k" to denote "kilo," which represents a factor of 1,000 or 1024 in the context of computer memory, followed by an uppercase "B" to signify that it is a byte (a unit of digital information). In computing, memory sizes are often expressed in bytes, and to clearly differentiate between bits and bytes, the capitalization is important.

The lowercase "k" indicates the metric prefix for one thousand, while uppercase "B" denotes bytes, thus avoiding any confusion with bits, which are sometimes represented with a lowercase "b." Therefore, "kB" effectively communicates the size of data being described.

While other options present variations of this notation, "kB" is the standard and widely accepted format used in computing and data storage contexts.