Task: Question Answering
Input (English): 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.
Output (English): 1