Earth's atmosphere is composed of about 78 percent of what gas? a. carbon dioxide c. water vapor b. oxygen d. nitrogen select the best answer from the choices provided

Option D; nitrogen

Earth's atmosphere consists of a number of gases. For example- nitrogen, oxygen, carbon dioxide, water vapor, methane, ozone, etc. The highest concentration is of nitrogen gas and accounts for 78 percent of the total volume. Next comes oxygen which is 21 percent. Remaining gases are present in the 1 percent share. This means water vapor and carbon dioxide is present in 1 percent share only.