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 radiopharmaceutical is used in Imaging of Reticulo endothelial system 
Select and explain. 
A. Tc-99m Red blood cells, B. Tc-99m Pyrophosphate, C. Tc-99m Sulfur Colloid, D. Tc-99m Teboroxime
C: Tc-99m Sulfur Colloid
Answer: C: Tc-99m Sulfur Colloid 
Explanation: Tc-99m Sulfur Colloid -Imaging of RES, Gastric emptying, GI bleeds.