Oligonucleotides are synthesized chemically. Which of the following step is involved in oligonucleotide synthesis?

A. Nucleotide addition is done by adding many nucleotides at a time

B. The coupling reaction should involve water

C. Only one type of nucleotides can be added at a time

D. Unblocking of the reactive groups leads to addition of nucleotides

Explanation: Oligonucleotide synthesis is done on the basis of blocking the reactive groups so that only one nucleotide is added as the unblocking is done. The coupling reaction should not involve water because than water will do nucleophilic reaction. A mixture of nucleotides can be added at a time.