It Is Difficult to Assess the Integrity of Cranial Nerve

It is difficult to assess the integrity of cranial nerve IX apart from X because:

A) cranial nerve IX mediates the gag reflex elicited at the base of the tongue,which is also a function of X
B) it is difficult to elicit the sensory portion of the pharyngeal gag reflex,which is the only function of cranial nerve IX
C) it is often the case that the sensory portion of the gag reflex is intact without a motor component
D) the vagus nerve has a larger role in the sensory and motor functions of the glossopharyngeal nerve
E) both B and D