Option A is the correct approach as it combines the Azure AI Translator service for text translation and the Azure AI Speech service for speech-to-text and text-to-speech conversion. This combination of services can enable the chatbot to understand and respond to user queries in multiple languages with speech-to-speech functionality. Option B is incorrect as Azure Cognitive Services is a broader category of services that includes both the Translator and Speech services. Option C is incorrect as it does not include the Azure AI Speech service, which is necessary for speech-to-speech functionality. Option D is incorrect as Azure Machine Learning is not directly related to speech-to-speech functionality.