A. 0 ÷ 28 = 0 True. 0 divided by anything other than 0 is 0.
B. 28 ÷ 0 = 0 False. Division by zero is undefined.
C. 28 − 0 = 0 True. Take zero away from 28, you still have 28.
D. 28 + 0 = 0 True. Add zero to 28, you still have 28.
"Division by zero is undefined" means that you cannot divide by zero since the division operation gives no result when you divide by zero.