14 16 17 18
I gave my students this multiple choice question: Hydrogen has an atomic mass of 1, and oxygen has an atomic mass of 16. When a water molecule forms, two hydrogen atoms combine with one oxygen atom. What is the mass of a water molecule?

Only one answer is correct among these 4 choices:
- 14
- 16
- 17
- 18

Could you tell me which one is correct?

18