Which of the following are regular sets?

Option A, {an b2m} | n≥0, m≥0}, is regular because it represents strings with any number of a's followed by an even number of b's, which can be recognized by a finite automaton. Option D, {xcy | x,y ∈ {a,b}*}, is regular as it describes strings containing exactly one 'c' surrounded by any combination of a's and b's, which is also regular. Options B and C involve conditions (n=2m and n≠m) that require counting, making them non-regular. Thus, only A and D are regular sets.