(d) Stock Market Analysis
Stock Market Analysis is not an NLP application. Sentiment Analysis, Speech Recognition, and Spam Filtering all involve processing natural language text or speech.
The textbook (Chapter 6) lists NLP applications as voice assistants, sentiment analysis, text classification, keyword extraction, language translation, and autogenerated captions. Spam filtering uses text classification (an NLP task), and speech recognition processes natural language. Stock Market Analysis is primarily a financial/statistical task, not an NLP application. Examiners expect direct identification of the odd one out with a brief reason.