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: Medicine
Which test uses oligomer with single base pair substitution as primer 
Select and explain. 
A. PCR, B. RFLP, C. Error coded mutation analysis with PCR, D. Site directed mutagenesis
D: Site directed mutagenesis
Answer: D: Site directed mutagenesis 
Explanation: D i.e. Site directed mutagenesis Site directed mutagenesis and oligonucleotide directed mutagenesis uses oligomer with single base pair substitution as primerQ to create a specific DNA sequence change (in gene), thus producing modified proteins with changes in primary structure of protein. This helps researchers to examine the effect of these changes on 3-D structure, folding & activity of protein.