Why Are the Complementary Base-Pairing Rules So Important When a Cell

Why are the complementary base-pairing rules so important when a cell needs to copy its DNA?

A) The cells need both strands to be accurate because each strand codes for one half of the gene.
B) As long as there is one strand, a copy can be made by following the pairing rules.
C) Unless the bases pair up correctly, the DNA strand can break apart.
D) Transcription cannot proceed unless the pairs are in the proper sequence.