Why Does a Replication Fork Have a Leading and Lagging

Multiple Choice

Why does a replication fork have a leading and lagging strand?

A) because DNA synthesis always goes from 5' to 3'
B) because DNA polymerase only attaches nucleotides to the 3' end of strands
C) because DNA synthesis can grow off of either the 3' or 5' end
D) because DNA synthesis always goes from 3' to 5'
E) Both answers, with DNA synthesis proceeding from 5' to 3', and DNA polymerase only acting on the 3' end, are correct.