60. Suppose that stacks and queues are provided as opaque data types, offering only operations to add elements, to
remove elements, and to test for emptiness. Suppose that a programmer wants to count the number of elements
in a given stack or queue C, which is currently in some state t, using only one auxiliary stack or queue D.
The structures C and D can be used in any way possible based on the methods they offer, but C must be
restored to its state t after counting its elements.
Counting elements as described above is possible for which of the following data types?
I. C is a queue and D is a queue.
II. C is a stack and D is a stack.
III. C is a queue and D is a stack.
(A) None (B) I and II only (C) I and III only (D) II and III only (E) I, II, and III
