What is the purpose of an application programming interface (API)?

An Application Programming Interface (API) is a set of protocols, routines, and tools that allow different software applications to communicate with each other. APIs provide the necessary instructions for one program to interact with another, enabling the integration of different systems and the development of new functionalities.

Option D: To provide a set of instructions that allow computer programs to communicate with each other is correct because it accurately describes the fundamental purpose of an API.