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: The metal that appears most frequently in the active site of metalloproteases is: 
 Options:  <1> Calcium. <2> Magnesium. <3> Selenium. <4> Sodium. <5> Zinc.
