Which polymerase is responsible for transcribing all protein-coding nuclear pre-mRNAs in eukaryotes?
RNA polymerase I
RNA polymerase II
RNA polymerase III
RNA polymerase IV
According to the text, RNA polymerase II in eukaryotes is responsible for transcribing precursor mRNA, known as heterogeneous nuclear RNA (hnRNA), which includes all protein-coding nuclear pre-mRNAs.
Option 2 is the correct answer.