You are presented with the quiz "The bonds of that which when heavy is Deuterium cause what to expand when it freezes?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "hydrogen bonds cause water to expand when it freezes" and "deuterium, or heavy hydrogen, is an isotope of hydrogen, or a hydrogen atom with a neutron added". 

So, what's the best answer to the question?


 

        water   