alcohols
Air contains abundant oxygen and trace amounts of hydrogen.
Carbohydrates.
In small amounts, yes. Magma contains some hydrogen from water that has been subducted into the mantle.
Helium gas, and trace amounts of Oxygen and Nitrogen.
No, like all organic matter meat contains carbon, but it also contains significant amounts of hydrogen, oxygen, and nitrogen with smaller amounts of many other elements.
Hydrogen.
Gasoline always contains carbon and hydrogen and usually also contains at least small amounts of oxygen, nitrogen, and sulfur.
DNA is very long and contains innumerable amounts of carbon, hydrogen, oxygen, nitrogen, and phosphorus.
Milk contains a number of different chemical compounds and a number of different elements making up those compounds. It does contain hydrogen, oxygen, and calcium as you state, but it also contains carbon, nitrogen, phosphorus, and smaller amounts of some other elements.
Polar regions produce the densest waters because of the cooling and freezing there.
It can be harmful in large amounts, but is relatively safe in low amounts.
The composition of the atmosphere of Saturn is almost entirely made up of hydrogen, at 97%, and helium, at 3%. It also contains trace amounts of methane, at about 0.05%.