Which term is used to denote putting a plan or proposal into effect?

The term used to denote putting a plan or proposal into effect is "implement." This verb specifically refers to the action of executing or carrying out a strategy, decision, or plan. When an idea or proposal is implemented, it means that the necessary steps are taken to make it a reality, demonstrating an application of a concept or plan in a practical manner.

In contrast, the other choices involve different actions. "Interpret" involves explaining or making sense of information, "extrapolate" refers to extending or projecting known information to predict or estimate unknown aspects, and "investigate" pertains to examining or inquiring into a subject thoroughly. Each of these terms addresses different cognitive processes, while "implement" specifically focuses on the execution phase of any proposed plan or initiative.