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: Pathology
Haematocrit is the ratio of: 
Select and explain. 
A. WBC to whole blood, B. Platelets to whole blood, C. RBCs to whole blood, D. Total blood cells to plasma
C: RBCs to whole blood
Answer: C: RBCs to whole blood 
Explanation: Haematocrit (also known as packed cell volume) is the volume percentage (%) of red blood cells in blood.