How does the pairing of the nitrogen bases in a dna molecule make sure that a replicated strand is exactly the same as the original strand?

What ensures that DNA molecule is replicated exactly as its original strand is with the ability of the DNA to make way and let the base pairs match with each base. This enables them to form the same strands so that it is identical and not different with the original strand.

1. efficient use of space

2. elimination of groundwater contamination

3. energy generation

4. lower carbon footprint