The combination of elements with atomic numbers 20 and 8 (A and Y, respectively) would result in the formation of an ionic compound, AY. Element 20 (A) is calcium, a metal that easily loses two electrons to form a stable Ca2+ ion. Element 8 (Y) is oxygen, a non-metal that readily accepts two electrons to form a stable O2- ion. When calcium (A) reacts with oxygen (Y), calcium loses two electrons to form Ca2+, and oxygen gains two electrons to form O2-. The oppositely charged ions, Ca2+ and O2-, are then held together by electrostatic forces of attraction to form the ionic compound, AY. Therefore, the correct option is: "an ionic compound, AY is formed."