Study the following program: // precondition: x>=0 public void demo(int x) {…

The function demo(x) is a recursive method that prints the last digit of x, calls itself with x divided by 10 (removing the last digit), and then prints the last digit again after returning. For demo(1234): First, it prints 4 (1234 % 10). Since 4!= 0, it calls demo(123). Inside demo(123), it prints 3, then calls demo(12). Inside demo(12), it prints 2, then calls demo(1). Inside demo(1), it prints 1, then calls demo(0). In demo(0), it prints 0. Since 0 % 10 == 0, the recursion stops and does not call demo(0) again. As each function returns, it prints its last digit again: 1 (from demo(1)), then 2 (from demo(12)), then 3 (from demo(123)), and finally 4 (from demo(1234)). The complete output sequence is 4, 3, 2, 1, 0, 0, 1, 2, 3, 4. Thus, the correct answer is D.