This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: DNB 2018, Subject name: Biochemistry
Sigma (s) subunit is present in: 
Select and explain. 
A. 80 S subunit, B. RNA polymerase, C. Required for initiation of replication, D. DNA polymerase
B: RNA polymerase
Answer: B: RNA polymerase 
Explanation: RNA POLYMERASE DNA dependent RNA polymerase Complex holoenzyme with five polypeptides units Five polypeptides - 2 alpha , 1b , 1b' , one sigma Sigma subunit enables the core enzyme to recognize and bind the promoter region to form the preinitiation complex (PIC). b-Main catalytic activity b' binds to DNA template