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: Social & Preventive Medicine
In a double blind clinical drug trial 
Select and explain. 
A. Each patient receives a placebo, B. Each patient receives both (double) treatments, C. The patients do not know which treatment they are receiving, D. The patients do not know that they are in a drug trial
C: The patients do not know which treatment they are receiving
Answer: C: The patients do not know which treatment they are receiving 
Explanation: None