Final answer:
When a method only requires a copy of an argument, it should be passed by value. This ensures that the method cannot alter the original variable or object but instead works with a copy.
Step-by-step explanation:
When a method just needs to use a copy of an argument passed to it, the argument should be passed by value. In many programming languages, passing by value means that the method receives a copy of the argument, not the actual variable itself. This is useful when you want to ensure that the original data is not modified by the method. Languages such as Java and C# handle primitive data types like integers and floats this way by default. However, for objects, many languages use a reference mechanism. In such cases, 'passing by value' may still refer to passing a copy of the reference, not the object itself, which means the method can still modify the original object. To truly pass a copy of an object, some languages provide mechanisms to explicitly clone or copy objects.