For an Object to Be Serialized and Unserialized,what Must Be

For an object to be serialized and unserialized,what must be true about the class definitions on the server and client?

A) They must have identical definitions,with the same class name and package.
B) The class names and definitions must match,but the packages may differ.
C) The class definitions must match,but the class name and package may differ.
D) The classes must have the same set of public properties,but the classes may have additional methods that differ and class name and package do not matter.