Explanation:

In computer terminology, abbreviations are commonly used for units of data storage. The abbreviation 'KB' stands for 'Kilobyte'. A Kilobyte is a unit of digital information storage, approximately $1000$ bytes or precisely $1024$ bytes ($2^{10}$ bytes). Options (a) 'Key Block', (b) 'Kernel Boot', and (d) 'Kit Bit' are not standard computer abbreviations for 'KB' in the context of data measurement. 'Key Block' might refer to a cryptographic concept, 'Kernel Boot' to the operating system startup process, and 'Kit Bit' is not a recognized term. Therefore, the correct meaning of KB is (c) Kilo Byte.