(Multiple choice) The statement

(setting one element equal to the next element) in a client program of the queue class 1. would cause a syntax error at compile time.
2. would cause a run-time error.
3. would not be considered an error by the computer, but would violate the encapsulation of the queue data type.
4. would be a perfectly legal and appropriate way to accomplish the intended task.

queue.items [1] = queue.items [2];