Java quiz. Which of the following options could be inserted i

Which of the following options could be inserted into (1) without causing compilation error


import java.util.*;

public class Test {
    public static void main(String[] args) {
        List<?> lst = new ArrayList<String>();
        // (1) Insert code here
    }    
}

lst.add(null);
lst.add("OK");
lst.add(127);
String v1 = lst.get(0);
Object v2 = lst.get(0);

Explanation

Since lst is List of values of unknown reference type, the only operations allowed are adding null (which is a correct value for all reference types) and reading into Object, as the last one is a parent for all reference types.