Java.util.Stack is a subclass of___. A. java.util.ArrayList B. java.util. LinkedList C. java.util.AbstractList D. java.util.Vector E. java util. List The keys must be unique for Map. True False Which of the following is correct to perform the set union of two sets 1 and s2? A. s1.union(s2) B. s1 + s2 C. s1. addAll(s2) D. s1.add(s2) Which of the following is correct to perform the set difference of two sets s1 and s2? A. s1 difference (s2) B. s1 - s2 C. s1.subtract(s2) D. s1.removeAll(s2) The Map is the base interface for___ A. TreeMap B. HashMap C. LinkedHashMap D. ArrayList E. LinkedList