What occurs during the elongation step of transcription?

During the elongation step of transcription, RNA polymerase plays a crucial role by synthesizing a new RNA strand complementary to the DNA template. It accomplishes this by adding ribonucleotides one by one, following the base-pairing rules. For example, if the DNA template has an adenine, RNA polymerase will add a uracil to the growing RNA strand. This process continues, resulting in the elongation of the RNA molecule until the polymerase reaches a termination signal. Thus, the correct answer highlights the primary action taking place during this phase of transcription, which is the addition of complementary bases to form the RNA transcript.