Which of the following best defines Natural Language Processing (NLP)?

Natural Language Processing (NLP) is best defined as an AI subfield that enables machines to read and interpret human language. This definition captures the essence of NLP, which involves the interaction between computers and humans through natural language. The goal of NLP is to assist machines in understanding, interpreting, and generating human language in a way that is both meaningful and contextually relevant.

NLP encompasses a variety of tasks, including language translation, sentiment analysis, speech recognition, and text summarization, all of which rely on the machine's ability to process and comprehend human language. By focusing on human language, NLP bridges the gap between human communication and computational understanding, allowing for smoother interactions between humans and machines.

The other options do not align closely with the core definition of NLP. For instance, while artificial neural networks play a role in many AI applications, they are a broader concept that extends beyond just language processing, as they are used in various domains, including image and sound processing, not limited to natural language. Enhancing visual data analysis pertains more closely to fields such as computer vision, and optimizing computational efficiency addresses algorithmic performance rather than focusing specifically on language understanding. Therefore, the chosen answer accurately reflects the primary function and nature of Natural Language Processing.