Question

78% of the air we breath is ______.
○ $n_2$ gas
○ oxygen
○ carbon
○ argon

Explanation:

Air composition: ~78% \( N_2 \) (nitrogen gas), ~21% oxygen, ~1% argon, CO₂, etc. Oxygen is ~21%, carbon isn't a major gas here, argon is ~1%. So 78% is \( N_2 \) Gas.

Answer:

A. \( N_2 \) Gas