Question

11/35
when you exercise, what gas does your body need more of?
blood
carbon dioxide
hydrogen
oxygen

Explanation:

During exercise, the body's metabolic rate increases, requiring more energy production. Cellular respiration, which produces energy (ATP), needs oxygen ($O_2$) to break down glucose. So the body needs more oxygen. Blood is not a gas, carbon dioxide is a waste product (produced more but not needed more), and hydrogen is not a primary gas needed for exercise - related respiration.

Answer:

D. Oxygen (assuming the options are labeled A: Blood, B: Carbon dioxide, C: Hydrogen, D: Oxygen)