Explanation:

In the context of computer science and digital storage, a kilobyte ($\text{KB}$) is conventionally defined as $2^{10}$ bytes. Let's analyze the options: Option (a) '1000 byte' is the SI (International System of Units) definition for 'kilo' ($10^3$), but in computing, this is often referred to as a kilobyte (decimal) or kibibyte ($\text{KiB}$) for $1024$ bytes. However, when 'kilobyte' is used without further qualification in computing, it almost always refers to $1024$ bytes. Option (b) '1024 byte' is precisely $2^{10}$ bytes, which is the standard definition of one kilobyte in computer memory and storage. This is the correct answer. Options (c) '10000 byte' and (d) '100000 byte' are incorrect values for a kilobyte. Option (e) 'None of these' is incorrect because option (b) is the correct equivalence.