Answer: Amazon Polly

**Explanation:** Amazon Polly is the correct AWS service for converting text into natural-sounding speech. Here's why: 1. **Amazon Polly** is AWS's Text-to-Speech (TTS) service that converts text into lifelike speech using advanced deep learning technologies. 2. **Key features relevant to the question:** - Supports multiple languages and voices - Provides natural-sounding speech output - Can be integrated into mobile applications - Offers neural text-to-speech (NTTS) for more natural speech patterns 3. **Why other options are incorrect:** - **Amazon Transcribe** (Option A): This is a speech-to-text service, converting audio to text, not text to speech. - **Amazon Translate** (Option C): This is a machine translation service for translating text between languages, not for speech synthesis. - **Amazon Comprehend** (Option D): This is a natural language processing (NLP) service for extracting insights and relationships from text, not for speech generation. For a mobile app that needs to read out user notifications in natural-sounding speech across multiple languages, Amazon Polly is the ideal AWS service choice.

Author: Jin H