(Multiple choice) The statement

(setting the top element equal to the second element) in a client program of the stack 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 stack data type.
4. would be a perfectly legal and appropriate way to accomplish the intended task.

stack.items [0] = stack.items [1];