The picture below shows the process of transcription.

During transcription, enzymes bind to a molecule of DNA. Then, the enzymes unwind and separate the DNA's double helical strands. As the molecule unwinds, complementary nucleotides pair with one of the DNA strands to form
A.
a DNA polymerase.
B.
a protein molecule.
C.
an identical strand of DNA.
D.
an RNA molecule.