A is incorrect: AI Search is primarily for indexing and querying data, not real-time audio processing and PII redaction.

B is incorrect: AI Vision focuses on image and video analysis, not real-time audio stream processing for PII.

C is incorrect: AI Translator is designed for language translation, not for identifying and redacting PII within an audio stream.

D is correct: The Azure Speech service is specifically engineered to detect and automatically remove sensitive personal data during the process of converting spoken words into text, including in live transcription scenarios.