Options :

1. 5’-phosphate of one nucleotide joins the 3’-hydroxyl of the next nucleotide

2. 3’-phosphate of one nucleotide joins the 3’-hydroxyl of the next nucleotide

3. 3’-phosphate of one nucleotide joins the 5’-hydroxyl of the next nucleotide

4. 5’-phosphate of one nucleotide joins the 5’-hydroxyl of the next nucleotide