Some problems with the digestive system make it very difficult for the body to digest enough food. Why would it be harder to exercise when you have a digestion problem like this? A. You would not be able to sleep, which would make you too tired to exercise.
B. Your cells would have molecules from air, but would not get enough molecules from food.
C. You would need to breathe in a lot more air because your body would have fewer molecules from food.
D. You would not get any of the molecules your cells need to exercise.

The answer to your question would be:

B, Your cells would have molecules from air, but would not get enough molecules from food.

You can actually use logic to riddle this answer out.

Option A is not plausible because sleep is out of the question. The answer has to be something related to the lack of something, such as a certain molecule, not sleep.

Option C would make no sense in any context. The fewer molecules of food sure, but it doesn’t mention having enough or too little molecules needed for exercise.

Option D is a no contest answer. If you have a problem digesting enough food, that means you would be lacking food molecules. The only way you could be able to lack both food molecules, and oxygen molecules, mean you have both respiratory problems and digest problems, or a disease that attacks both the respiratory system and digestive system.

I hope this helps you out