This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Channelopathies and Neuropathies, Subject name: Medicine
The gag reflex is checked in a 65-year-old woman with diabetes mellitus. When the right side of the pharynx is touched with a tongue blade, the palate elevates symmetrically. When the left side of the pharynx is touched, the palate does not elevate at all.Which of the following cranial nerves is most likely to be responsible for this? 
Select and explain. 
A. 8th cranial nerve, B. 9th cranial nerve, C. 10th cranial nerve, D. 12th cranial nerve
B: 9th cranial nerve
Answer: B: 9th cranial nerve 
Explanation: * 9th nerve form the Afferent pathway - Receives stimulus * 10th nerve form the Efferent pathway - Elevates pharynx Afferent i.e 9th is affected on left side Right Side Left Side A:[?] 9th A:x E:[?] 10th E:[?] 10th