Which of the following is an action that prevents an event from happening?

The correct answer, "thwart," refers to an action that actively prevents or obstructs an event from occurring. In various contexts, to thwart means to stop something from happening, often by taking deliberate steps or interventions. For instance, if someone is trying to carry out a plan that is harmful or undesirable, to thwart that plan would mean applying efforts to ensure it does not succeed.

In contrast, the other options do not align with the concept of preventing an event. Retaliating implies responding to an action, typically in a manner intended as revenge, rather than stopping it altogether. Compromising usually involves making concessions to reach an agreement or resolve a conflict, rather than preventing an occurrence. Cooperating signifies working together towards a common goal or purpose, which might support the execution of an event rather than preventing it. Thus, "thwart" stands out as the action that specifically embodies the idea of prevention.