4a) 4b) 4c) List the three key differences between arrays and ArrayLists in Java. (3 marks) Consider a class with a field variable xs declared by ArrayList xs; Write a method alternating that removes alternating elements from xs. For example, if xs is , after alternating has run, xs will be {"A", "C", "E"). Similarly, if xs is , after alternating has run, xs will be {"A", "C", "E"). (4 marks) // removes alternating elements from the field variable xs public void alternating () Describe how alternating would have to be written if xs were an array variable instead of an ArrayList. What issues might this cause? (3 marks)