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: Pharmacology
Antihistaminic used in motion sickness is : 
Select and explain. 
A. Cetirizine, B. Meclizine, C. Diphenhydramine, D. Fexofenadine
C: Diphenhydramine
Answer: C: Diphenhydramine 
Explanation: Diphenhydramine and promethazine have maximum anti-cholinergic activity and maximum ability to cross the blood-brain barrier and are thus most effective in motion sickness.