Hydrogen bonds cause water to expand when it freezes.
Deuterium, or heavy hydrogen, is an isotope of hydrogen, or a hydrogen atom with a neutron added.
The bonds of that which when heavy is deuterium cause water to expand when it freezes.
The bonds of that which when heavy is Deuterium cause what to expand when it freezes?

(1) matter
(2) rings
(3) CO 2
(4) liquids
(5) gas
(6) solutes
(7) cations
(8) water