In programming, what term describes a specific action taken in response to an event?

The term that best describes a specific action taken in response to an event is "Handler." In programming, a handler typically refers to a function or a block of code that is executed when a specific event occurs, such as a user clicking a button, a mouse moving, or a key being pressed. This allows the program to react dynamically to user input or other occurrences.

When an event is triggered, the handler is invoked to carry out the necessary actions associated with that event, making it an essential concept in event-driven programming. The other terms listed do not encapsulate this concept as accurately as "Handler." For instance, "Action" is a broader term that doesn't specifically refer to the context of responding to an event, while "Response" can imply a reaction but lacks the specificity of an implemented function. "Execution" pertains generally to running code but does not specifically denote the association with events like a handler does. Thus, "Handler" is the most precise and relevant term in this context.