Explanation:

The fundamental building block of digital information in computing is the bit. Option (a) 'digit' is too general; it could refer to decimal digits ($0-9$), which are not the smallest unit a computer *understands* at its most basic level. Option (b) 'kilobyte' ($\text{KB}$) is a much larger unit, equivalent to $1024$ bytes or $8192$ bits. Option (c) 'bit' is an abbreviation for 'binary digit' and represents the smallest unit of data in a computer, capable of holding a single binary value ($0$ or $1$). This is the correct answer. Option (d) 'byte' is a collection of $8$ bits, making it a larger unit than a bit. Option (e) 'none of these' is incorrect because option (c) correctly identifies the smallest unit of information.