The correct answer is: A. (m+1) full adders.
A full adder is a digital circuit that performs addition on two single-bit numbers and produces a sum and a carry bit. A parallel adder is a digital circuit that performs addition on two multi-bit numbers simultaneously. The number of full adders required to build a parallel adder is equal to the number of bits in the numbers being added plus one.
For example, a 4-bit parallel adder would require 5 full adders: one for the carry bit, and one for each of the four bits in the numbers being added.
Option B is incorrect because it divides the number of bits in the numbers being added by 2. This would only be correct if the numbers being added were both even.
Option C is incorrect because it subtracts 1 from the number of bits in the numbers being added. This would only be correct if the numbers being added were both odd.
Option D is incorrect because it is the number of bits in the numbers being added. This would only be correct if the numbers being added were both 1 bit long.
Option E is incorrect because it is not a valid option.