Which AWS service is designed to help users build conversational interfaces into applications using voice...

A is correct because Amazon Lex is the AWS service that helps users build conversational interfaces into applications using voice and text. B is incorrect because Amazon Transcribe is the AWS service that helps users convert speech to text. C is incorrect because Amazon Comprehend is the AWS service that helps users analyze text using natural language processing. D is incorrect because Amazon Timestream is the AWS service that helps users collect, store, and process time series data.