During DNA replication a DNA polymerase adds nucleotides away from the replication fork. b DNA polymerase adds nucleotides in the 5' to 3' direction. c a primer is required on the lagging strand. d All the above are true.

d). All the above are true.

Explanation: DNA replication is a process by which cells make two identical copies of the DNA. It is a process of copying the cell's DNA into two identical new DNA molecules. This process is catalyzed by an enzyme known as DNA polymerase. DNA replication begins at the replication fork where the DNA is unwound and each strand serves as a template for the synthesis of a new strand. The synthesis of the new strands requires a primer (a short RNA strand) to which new nucleotides are attached. The synthesis of the new strand occurs in the 5'->3' direction. Addition of the nucleotide in the leading strand occurs continuously and in the direction of the replication fork movement while the addition of nucleotides in the lagging strand occurs semidiscontinously and proceeds in the direction opposite to the direction of the replication fork movement.