<span>The right answer is the option B. Close to 99 percent. The atmosphere is a mixture of gases: nitrogen, oxygen, CO2, H2O, argon, among others. Nitrogen is about 78% and oxygen is about 21%, so they two together constitute about 99 percent of the Earth's atmosphere.</span>
D) physical and chemical changes
1.D 2.C 3.B 4.A is the answer i believe you're looking for.
Answer:
it improves the accuracy of the results
