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
[{'content': 'Carbenicillin : \nSelect and explain. \nA. Is effective in pseudomonas infection, B. Has no effect in Proteus infection, C. Is a macrolide antibiotic, D. Is administered orally', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]