Which of the following states the correct atmospheric percentages of the major gases?

The correct answer, which states that nitrogen makes up approximately 78% of the Earth's atmosphere and oxygen accounts for about 21%, reflects the actual composition of the atmosphere. Nitrogen is the most abundant gas, essential for various biochemical processes and providing an inert backdrop that dilutes oxygen and other reactive gases. Oxygen is crucial for aerobic respiration and combustion processes.

The other provided percentages do not accurately represent the atmospheric composition: oxygen does not make up as much as 78%, which is far too high; carbon dioxide is indeed present, but its concentration is only about 0.04%, making it an insignificant percentage compared to nitrogen and oxygen; and stating that nitrogen is 70% and oxygen 30% also misrepresents the known proportions.