(c) NLP
Email filters, spam filters, and smart assistants are real-world applications of Natural Language Processing (NLP).
The source passages (Chapter 6, Section 6.2) list voice assistants (smart assistants like Siri, Alexa, Google) as key NLP applications. Email/spam filters also use NLP to classify and process text. Examiners expect you to directly identify the correct option and briefly justify it in one line.