Answer the following question given this paragraph: 

Water is an example of a common chemical compound. As you can see in the Figure below , each water molecule consists of two atoms of hydrogen and one atom of oxygen. Water always has this 2:1 ratio of hydrogen to oxygen. Like water, all compounds consist of a fixed ratio of elements. It doesn’t matter how much or how little of a compound there is. It always has the same composition.


Q: What molecule consists of two atoms of hydrogen and one atom of oxygen?

 Choices:

- carbon monoxide

- hydrogen peroxide

- air

- water

A:
water
