This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Which of the following groups of contrast agents may be safely injected intrathecally? \nSelect and explain. \nA. Water-soluble ionic monomers, B. Water-soluble non-ionic monomers, C. Water-soluble ionic dimers, D. Oil based iodinated contrasts', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Most of the water soluble iodinated contrast media of the non ionic low osmolar class is safe to use intrathecally', 'role': 'assistant'}]