Answer : The correct answer is -
(A) Turning on gene expression.
Gene expression corresponds to the transcription (DNA to mRNA) and translation (mRNA to protein) of gene (which is a segment of DNA, coding for certain protein) so as to form a particular protein or polypeptide.
It involves two steps that are Transcription and translation.
Gene expression can be turned on by the activation of certain protein molecules, known as transcription factors that bind to specific region in the DNA and increase the production of protein.
It means that Protein synthesis can be increased by turning on gene expression.
Thus, option A) is the right answer.