An Array is used to store multiple variables in the memory in the continuous memory allocation on which starting index value is starting from 0 and the last index value location is size-1.

In java programming language the array.length is used to tells the size of the array so when the user wants to get the value of the last element, he needs to print the value of (array.length-1) location so the correct statement for the java programming language is to print the last element in the array named ar is--

System.out.println(ar[ar.length-1]);

No option provides the above statement, so option d (None of these) is correct while the reason behind the other option is not correct is as follows--

Option a will prints the size of the array.
Option b also gives the error because length is an undeclared variable.
Option c will give the error of array bound of an exception because it begs the value of the size+1 element of the array.