What is the expression for even parity for 3 bits a, b, c ?

Even parity ensures the total number of 1s in a data set is even. For three bits a, b, and c, the parity bit must be chosen such that when added to these bits, the count of 1s remains even. The XOR operation (⊕) outputs 1 if an odd number of inputs are 1, and 0 otherwise. Therefore, the expression a ⊕ b ⊕ c evaluates to 1 if there are an odd number of 1s among a, b, and c. To achieve even parity, this result must be the parity bit itself if we consider the system where the sum of all bits (including parity) must be even. However, in standard terminology for generating a parity bit p such that (a + b + c + p) is even, if the data bits have an odd number of 1s (XOR sum = 1), p must be 1. If the data bits have an even number of 1s (XOR sum = 0), p must be 0. Thus, the parity bit is simply a ⊕ b ⊕ c. Option B represents odd parity (the complement). Options C and D represent AND and OR operations, which do not count the number of 1s to ensure evenness.