Is the set of multiples of 4 closed under addition? Explain why or provide a counterexample if not.

A. Yes, because the sum of any two multiples of 4 is also a multiple of 4.


B. Yes, because the sum of any two multiples of 4 is also a multiple of 8.


C. No, and a counterexample is –4 + (–8) = –12.


D. No, and a counterexample is 26 + 16 = 42.