According to the Microsoft Azure AI Fundamentals (AI-900) official study guide and the Microsoft Learn module “Identify features of speech capabilities in Azure Cognitive Services”, the Azure Speech service provides functionality for converting text to spoken words (speech synthesis) and speech to text (speech recognition).

In this scenario, the app must read recipe instructions aloud to assist users with visual impairments. This task is achieved through speech synthesis, also known as text-to-speech (TTS). The Azure Speech service uses advanced neural network models to generate natural-sounding voices in many languages and accents, making it ideal for accessibility scenarios such as screen readers, virtual assistants, and educational tools.

Microsoft Learn defines Speech service as a unified offering that includes:

Speech-to-text (speech recognition): Converts spoken words into text.

Text-to-speech (speech synthesis): Converts written text into natural-sounding audio output.

Speech translation: Translates spoken language into another language in real time.

Speaker recognition: Identifies or verifies a person based on their voice.

The other options do not fit the requirements:

A. Text Analytics – Performs text-based natural language analysis such as sentiment, key phrase extraction, and entity recognition, but it cannot produce audio output.

B. Translator Text – Translates text between languages but does not generate speech output.

D. Language Understanding (LUIS) – Interprets user intent from text or speech for conversational bots but does not read text aloud.

Therefore, based on the AI-900 curriculum and Microsoft Learn documentation, the correct service for converting recipe text to spoken audio is the Azure Speech service.

✅ Final Answer: C. Speech