The correct answer is: B. a mixture of carbon dioxide and nitrogen
Exhaled air contains about 4% carbon dioxide, 78% nitrogen, 16% oxygen, and 4% other gases. The percentage of carbon dioxide in exhaled air is higher than the percentage of carbon dioxide in inhaled air, which is about 0.04%. This is because our bodies use oxygen to produce energy, and as a byproduct of this process, we produce carbon dioxide. The carbon dioxide is then exhaled out of our lungs.
The percentage of nitrogen in exhaled air is about the same as the percentage of nitrogen in inhaled air. This is because nitrogen is not used by our bodies, and it passes through our lungs unchanged.
The percentage of oxygen in exhaled air is lower than the percentage of oxygen in inhaled air. This is because our bodies use oxygen to produce energy, and as a byproduct of this process, we produce carbon dioxide. The oxygen is then exhaled out of our lungs.
The percentage of other gases in exhaled air is very small. These gases include water vapor, argon, and carbon monoxide.
I hope this helps!