Answer:
Through their lungs.
Explanation:
They need lungs to take in oxygen and oxygen is vital for survival.
Most gases are invisible. Give it some thought. Like 2 gases your body use to breathe. The noble gases on the periodic table. The most abundant gas in the Earth's atmosphere. The one everyone is concerned about being affected by global warming. The poisonous one in some people's houses.
point b i think, because you have to see the amount of steepness in the slope.
