Question 2
In a carbohydrate, hydrogen and oxygen are always combined in which ratio?
The right answer is the one marked above.
Hydrogen to oxygen is always 2 : 1 — two hydrogen atoms for every one oxygen atom, exactly as they are in water.
That is where the name comes from: carbon plus hydrate. Glucose is C6H12O6 — 12 hydrogen, 6 oxygen, and 12 : 6 is 2 : 1.