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: Biochemistry
True among all is 
Select and explain. 
A. Repressor is dimer and a positive regulator, B. CRP is gratuitous inducer, C. Lactose is positive regulator, D. Catabolite repression is mediated by CRP
D: Catabolite repression is mediated by CRP
Answer: D: Catabolite repression is mediated by CRP 
Explanation: Catabolite repression is mediated by CRP