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 requires more muscle effort. Muscles need energy (from cellular respiration, which needs oxygen), so more oxygen is needed, leading to heavier breathing.

The other options are incorrect: The body doesn't have too little CO₂ (it produces more with increased activity), the body can't use CO₂ for energy, and blood pressure typically increases (not decreases) during physical exertion to pump more blood to muscles.

Answer:

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