Indicating that a parameter is 'Replaces' mode, What does it mean?
1) means that the parameter's value might be changed from its incoming value in a way that depends on its incoming value
2) means that the outgoing value, in fact the entire behavior of the method, is independent of the incoming value of that parameter
3) is equivalent to adding 'and x = #x' to the ensures clause
4) is equivalent to adding 'and x = #x' to the requires clause