18. Name THREE covalent modifications typically made to an RNA molecule in
eukaryotic cells before the RNA molecule becomes a mature mRNA.

The pre-mRNA molecule undergoes three main modifications. These modifications are 5' capping, 3' polyadenylation, and RNA splicing, which occur in the cell nucleus before the RNA is translated.

answer; i believe that the correct answer is(d) nondisjunction during meiosis;