What distinguishes an API from a Web Service?

• A. All APIs are Web Services
• B. Web services can operate without a network
• C. APIs are specifically designed for REST only
• D. All Web services are APIs but not all APIs are Web services

Answer: (D)

The distinction between APIs and web services is rooted in their definitions and functionalities. The chosen answer clarifies that while all web services qualify as APIs due to their capability to facilitate communication and enable application interaction, not all APIs are necessarily web services.

APIs, or Application Programming Interfaces, serve as sets of rules and protocols for building software applications, enabling different software entities to communicate with each other. They can exist in various forms, including local APIs that do not rely on the web for operation.

On the other hand, web services are a specific subset of APIs that function over the internet, utilizing standard protocols such as HTTP, XML, and JSON to enable this communication. They are designed to support machine-to-machine interactions over a network.

It's important to recognize that web services inherently fulfill the role of an API while being constrained to network-based communication. In contrast, the broader category of APIs can encompass non-network interfaces, making the identified answer accurate in highlighting this relationship between the concepts.