Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: It usually protects the DNA of a restriction enzyme: 
 Options:  <1> Methylation of a nitrogenous base. <2> Glycosylation of a nitrogenous base. <3> Acetylation of deoxyribose. <4> Phosphorylation of deoxyribose. <5> Loss of one of the hydroxyl groups of phosphate.
