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
Which of the following groups of contrast agents may be safely injected intrathecally? 
Select and explain. 
A. Water-soluble ionic monomers, B. Water-soluble non-ionic monomers, C. Water-soluble ionic dimers, D. Oil based iodinated contrasts
B: Water-soluble non-ionic monomers
Answer: B: Water-soluble non-ionic monomers 
Explanation: Most of the water soluble iodinated contrast media of the non ionic low osmolar class is safe to use intrathecally