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: Radiology
Which of the following contrast agents is preferred in a patient with a decreased renal function to avoid contrast nephropathy – 
Select and explain. 
A. Acetylcystine, B. Fenoldapam, C. Mannitol, D. Low osmolar contrast
D: Low osmolar contrast
Answer: D: Low osmolar contrast 
Explanation: Low osmolar contrast agents are the contrast agents of choice in patients with pre-existing renal insufficiency.
Acetylcysteine and fenoldopam may also be used to reduce contrast-induced nephropathy but these are not contrast agents. Further, these drugs have limited value for their use for this indication