Final answer:
Auguste Comte believed that the engine of social progress was scientific inquiry and rational thinking, which corresponds to answer A.
Step-by-step explanation:
Auguste Comte, the French philosopher, is known for creating the field of sociology and for advancing a theory of social progress. Comte believed that the engine of social progress was rooted in the application of scientific inquiry and rational thinking.
He proposed a 'law of three stages' in the development of societies, with the final stage, positivism, characterized by a focus on scientific understanding of the natural and social world. According to Comte, this would lead to human progress by empirically addressing social problems.