Which of the following is a collective noun for guns?

Battery

The answer is battery. A battery of guns is a group of guns that are fired together. The word "battery" is also used to refer to a group of artillery pieces, but it can also be used to refer to a group of guns.

The other answer choices are incorrect. Troupe refers to a group of actors, bunch refers to a group of things that are loosely associated, and ammunition refers to the bullets or shells that are fired from guns.