Ans (b).  DNA polymerase adds deoxyribonucleotides to the free '-end of the growing polynucleotide chain so, that replication of the 3'$\to$5' strand of the DNA molecule is continuous (growth of the new strand in 5'$\to$3' direction).

Since DNA dependent DNA polymerase catalyzes polymerization only in one direction (5'$\to$3'), discontinuous synthesis of DNA occurs in the other strand.