Question

select all the correct answers.
jon likes hiking. he observes that whenever he hikes up a hill, he breathes heavier than when he is on flat ground. which two statements explain why this happens?
sensors in the brain detect a lack of oxygen.
the muscles in his body need more energy and therefore more oxygen.
the body has too little carbon dioxide to maintain function.
the body is using carbon dioxide instead of oxygen to make energy.
blood pressure has decreased, so less blood is being pumped to the muscles.

Explanation:

1. For "Sensors in the brain detect a lack of oxygen": When hiking uphill, the body's oxygen demand increases. If oxygen levels drop, brain sensors detect this and trigger heavier breathing to get more oxygen.
2. For "The muscles in his body need more energy and therefore more oxygen": Hiking uphill is more strenuous, so muscles require more energy (produced via cellular respiration which needs oxygen), increasing oxygen demand and causing heavier breathing.

Other options are incorrect: The body needs carbon dioxide (but not too little to cause this), the body uses oxygen (not CO₂) for energy, and blood pressure typically doesn't decrease in this context (muscles need more blood, so blood pressure may adjust to supply more, not less).

Answer:

• Sensors in the brain detect a lack of oxygen.
• The muscles in his body need more energy and therefore more oxygen.