3.4.2- Explain the significance of complementary base pairing in the conservation of the base sequence of DNA.
Complementary base pairing is significant because you have to make sure that the old base structure is preserved. DNA has to be an "exact copy" of the template. If this is messed up, mutaions can result.

3.4.3- State that DNA replication is semi-conservative.
DNA replication is semi-conservative because each new molecule formed by replication uses one new strand and one old strand which is conserved from the parent DNA molecule.