This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Medicine
A patient with clustered white lesions on the buccal mucosa opposite the upper 1st and 2nd molars pathognomonic for measles. These are 
Select and explain. 
A. Leukoplakia, B. Koplik spots, C. Kaposi spots, D. None
B: Koplik spots
Answer: B: Koplik spots 
Explanation: Koplik&;s spots: Little spots inside the mouth that are highly characteristic of the early phase of measles (rubeola). The spots look like a tiny grains of white sand, each surrounded by a red ring. They are found especially on the inside of the cheek (the buccal mucosa) opposite the 1st and 2nd upper molars. ref : harrisons 21st ed