In a nucleus,the number of ribonucleoside triphosphates is $10$ times the number of deoxyribonucleoside triphosphates,but only deoxyribonucleotides are added during $DNA$ replication. Suggest a mechanism.

(N/A) $DNA$ polymerase is the enzyme responsible for $DNA$ replication. It possesses a highly specific active site that can only bind and incorporate deoxyribonucleoside triphosphates $(dNTPs)$ into the growing $DNA$ strand. It cannot accommodate ribonucleoside triphosphates $(rNTPs)$ because the $2'$-$OH$ group present in the ribose sugar of $rNTPs$ creates steric hindrance,preventing them from fitting into the active site of the $DNA$ polymerase enzyme.