Final answer:
The patient is likely suffering from Measles (Rubeola) based on the symptoms described(option a).
Step-by-step explanation:
The patient in question is presenting with a cephalocaudal spread of maculopapular rash along with fever and possibly arthralgias/arthritis. Based on this information, the most likely diagnosis is option a)Measles (Rubeola).
Measles typically presents with a rash that starts on the face and spreads to the extremities, which matches the cephalocaudal spread mentioned. Additionally, the rash is raised and macular, fitting the description of a maculopapular rash.