Are there two answers to this question?

[NFuller]

The correct answer has been explained in detail by several members. @jbriggs444 has given examples of objects with fixed shape but not fixed volume and explained why this is a poor answer. If the OP is unsatisfied with these explanations, then I would recommend that he or she ask their instructor or search google for another explanation.

In any case, the original question has been answered and I think this thread has run its course.