What of the following happens first? a. Introns are edited out of the premature RNA ... b. RNA polymerase reaches a terminator region ... c. Nucleotides are covalently linked together ... d. RNA polymerase binds to a promoter region of DNA ...

The answer is RNA polymerase binds to a promoter region of DNA.

A promoter region of DNA is the site of initiation of gene transcription. For transcription to start, firstly, RNA polymerase must bind to a promoter region of DNA. RNA polymerase is an enzyme responsible for a synthesis of RNA and it enables nucleotides to covalently link together. When RNA polymerase reaches a terminator region, premature RNA frees. Further, introns are edited out of the premature RNA, and mature RNA is synthesised.