Naichen, I would say:
true a) ... or that, are good at depicting the behavior of an object across
ONE use cases, too. I guess what that emphasis is the importance of organization all development efforts around use ceases.
true b) state diagrams describe the states of particular object so it might be an overhead to create them for all the objects in the system, event this with little number of uninteresting states.
Honestly I am not sure what is this question suppose to test? false c) again, state diagrams describe the states of
ONE object
true d) why not, user interface or control objects are as good as any.
>> Could interface have several states?
I would thing so, but it would be rather states of an object implementing this particular interface. If it is "very interesting" (read complicated) interface it would make perfect sense to have state diagram focused on it.
>> what interface can have just some operations, right?
I am not quite certain if I have understood You but if you asking if interface can have attributes, the answer is positive, otherwise dealing with concepts like
Java interfaces would be rather complicated.