Which one of the following is the chemical name of heavy water ?

Which one of the following is the chemical name of heavy water ?

Hydrogen oxide
Deuterium dioxide
Deuterium oxide
Heavy hydrogen oxide
This question was previously asked in
UPSC CAPF – 2017
Heavy water is a form of water in which the hydrogen atoms are replaced by deuterium, an isotope of hydrogen with one proton and one neutron (compared to normal hydrogen, protium, which has one proton and no neutrons). The chemical formula for heavy water is D₂O or ²H₂O. The standard chemical name for D₂O is Deuterium oxide.
Heavy water is water composed of deuterium and oxygen. Deuterium is an isotope of hydrogen.
Heavy water is used primarily as a moderator and coolant in certain types of nuclear reactors (specifically, Pressurized Heavy-Water Reactors like the CANDU reactor) because deuterium absorbs fewer neutrons than normal hydrogen.