The most important is the oxygen.
oxygen
oxygen
oxygen
Oxygen, the upper one in group 16
The most important are carbon and oxygen.
It is the most stable form of oxygen as an element.
Oxygen is itself a chemical element.
Oxygen is by far the most abundant element in the Earth's crust, so naturally there are going to be a lot of metal oxides.
Oxygen is a representative element because it belongs to a group. Also, it is not situated in the transition metals area, and most importantly, it's not a metal!
oxygen
Oxygen
helium