This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
[{'content': 'Alcaftadine trial used this concentration of drug: \nSelect and explain. \nA. 5%, B. 1%, C. 0.25%, D. 2.50%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: * ALCAFTADINE is a H1 receptor antagonist, and can be used for allergic conjunctivitis* The trial done for alcaftadine used 0.25% solution.* The trial states: "When Alcaftadine was tested against placebo and olopatadine, only Alcaftadine 0.25% was shown to have a clinically significant reduction in conjunctival redness scores 7 and 15 minutes after administration\'', 'role': 'assistant'}]