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: Pharmacology
MDR gene acts by: 
Select and explain. 
A. Block drug activation, B. Block intracellular DNA synthesis, C. Cause efflux of drug, D. DNA repair inhibition
C: Cause efflux of drug
Answer: C: Cause efflux of drug 
Explanation: Cause efflux of drug