This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Sour taste is mediated by 
Select and explain. 
A. Na+ selective channel (ENac), B. G - protein coupled receptors, C. H+ ions permeable to ENaCs, D. Glutamate receptors
C: H+ ions permeable to ENaCs
Answer: C: H+ ions permeable to ENaCs 
Explanation: Salt ⇒ mediated by Na+ selective channel (ENaC)
Sour ⇒ mediated by H+ ions permeable to ENaCs
Bitter, sweet, umami ⇒ mediated by G-protein coupled receptors