This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Which is a reverse transcriptase? 
Select and explain. 
A. Topoisomerase 2, B. Telomerase, C. RNA polymerase 2, D. DNA polymerase alpha
B: Telomerase
Answer: B: Telomerase 
Explanation: Telomerase, a multisubunit RNA template-containing complex related to viral RNA-dependent DNA polymerases (reverse transcriptases), is the enzyme responsible for telomere synthesis and thus for maintaining the length of the telomere. Since telomere shoening has been associated with both malignant transformation and aging, this enzyme has become an attractive target for cancer chemotherapy and drug development.Ref: Harper&;s Biochemistry; 30th edition; Page no: 375