(A) Cells make proteins
Proteins are composed of amino acids. Proteins are made in a process called translation, in which the cell commands.
(B) RNA molecules copied before mitosis begins
DNA molecules are copied before mitosis, not RNA.
(C) mRNA molecules are transcribed to form tRNA
DNA is used as template to form both mRNA and tRNA in a process called transcription.
(D) polypeptides are made into mRNA
mRNA is the template used to make polypeptides in a process called translation.
Therefore, A is the right answer.
