Answer: RNA polymerase.
Explanation:
Transcription involves formation of mRNA molecules by information present in template DNA strand. Enzyme which starts the process of transcription is RNA polymerase that adds ribonucleotides to the growing RNA chains complementary to template DNA.
The mRNA carries informnation from nucleus to ribosomes, present in cytosol, where translation takes place.
Thus, the correct answer is option (A).
