Final answer:
The prominent Muslim doctor credited with the first accurate diagnosis and description of measles and smallpox is Al-Razi, also known as Rhazes.
Step-by-step explanation:
The greatest Muslim doctor who is credited as the first to diagnose and correctly describe measles and smallpox is b) Al-Razi (Rhazes). Al-Razi, also known as Rhazes, was an influential Persian polymath and a prominent figure in Islamic medicine. He made many contributions to the fields of medicine, chemistry, and philosophy. Among his contributions, he is particularly known for differentiating between smallpox and measles, diseases that were previously thought to be a single affliction. Al-Razi's work on smallpox and measles demonstrates his empirical approach to medicine, and his findings were significant in the development of early diagnoses for these diseases.