Answer:
In addition to the 10 carbon atoms, a molecule of this carbohydrate could also contain 10 oxygen, and 20 hydrogen atoms.
Explanation:
Think about the word "carbohydrates." The prefix "carbo-" indicates that there are carbon atoms in this compound. On the other hand, the "-hydrate" part of the name hints that this compound also contains hydrogen and oxygen (the two elements that form water.) That's exactly the case- carbohydrates contain exactly three elements: carbon, hydrogen, and oxygen. That rules out the second and the fourth choice: the molecule can't be a carbohydrate if it contains nitrogen atoms.
In particular, for this molecule to be a carbohydrate, the ratio between the number of H and O atoms in it should be the same as that in water. In a water molecule, there are twice as many H atoms as O atoms. So is the case in a carbohydrate molecule.
Among all four choices, only the third one meets both requirements. The molecular formula of this carbohydrate would be [tex]\rm C_{10} H_{20} O_{10}[/tex], which is equivalent to [tex]\rm C_{10}(H_{2}O)_{10}[/tex]. Hence the name "carbohydrate."
