Answer: Option A
:
A
DNA polymerase can add nucleotides only to the free 3’ ends of RNA primers. However, both the strands of a DNA double helix run along opposite directions, and thus, the synthesis of one strand (the leading strand) happens much easier than that of the other strand (lagging strand). DNA polymerase can add nucleotides only to the free 3’ end of an existing RNA primer. For the synthesis of the lagging strand, since the template runs along the 5’$\to$ 3’ direction, DNA polymerase adds nucleotides to already existing RNA primers (added by primase) to form short segments (about 100-200 nucleotides long in eukaryotes and 1,000-2,000 nucleotides long in bacteria). These segments are known as Okazaki fragments. DNA ligase does the final touch up by sealing the nicks between the fragments, to give rise to the new 3’$\to$ 5’ strand.