Correct option (b) lagging strand
Explanation :
When the double helix of DNA unwinds, DNA replication on one of the two strands (3' to 5' strand) can easily proceed continuously in 5' to 3' direction. This is the leading strand. On the other strand (5'- 3') if the synthesis has to take place in 5' to 3'direction. it has to be synthesized in a direction opposite to that on the leading strands. This strand is the lagging strand and on this strand synthesis takes place in segments discontinuously and these segments are then fused to create an intact lagging strand. This behaviour where the leading strand is synthesized continuously and the lagging strand is synthesized discontinuously is called semi - discontinuous replication.
