The correct answer is B. 256.
A byte is a unit of digital information that consists of eight bits. A bit is the smallest unit of information in computing and can be represented by a 0 or a 1. Eight bits can be used to represent 256 different values, from 0 to 255. This is because 2 to the power of 8 is 256.
Option A is incorrect because 16 is not a power of 2. Option C is incorrect because 128 is not a power of 2. Option D is incorrect because 255 is not a power of 2. Option E is incorrect because B is the correct answer.