_____ makes up approximately 78% of the air.

_____ makes up approximately 78% of the air.

• A. Oxygen
• B. Argon
• C. Carbon Dioxide
• D. Nitrogen

Answer: (D)

The question is about which gas is present in the largest amount in Earth's atmosphere. In dry air, nitrogen is the most abundant component, making up about 78 percent of the air by volume. Oxygen is the next most abundant at around 21 percent. The remaining gases, like argon and carbon dioxide, exist only in trace amounts. So nitrogen is the correct choice because it dominates the composition of air by volume, far more than the others listed. The other options are present in much smaller proportions.

The question is about which gas is present in the largest amount in Earth's atmosphere. In dry air, nitrogen is the most abundant component, making up about 78 percent of the air by volume. Oxygen is the next most abundant at around 21 percent. The remaining gases, like argon and carbon dioxide, exist only in trace amounts. So nitrogen is the correct choice because it dominates the composition of air by volume, far more than the others listed. The other options are present in much smaller proportions.