A library needs to automatically categorize electronic books by analyzing their content. Which AWS service should they use?

Amazon Comprehend is the correct choice because it is a natural language processing (NLP) service that uses machine learning to find insights and relationships in text. It can identify entities, key phrases, language, sentiments, and topics, making it ideal for automatically categorizing electronic books based on their content. Amazon Redshift is a data warehousing service, not designed for text analysis. Amazon CloudSearch is a managed search service, primarily for adding search capabilities to applications, not for content categorization. Amazon Aurora is a relational database service, which stores data but does not analyze its content in this manner.