Answer:
1. 380 parts per million (0.038%)
Step-by-step explanation:
By volume, dry air, which makes up the earth's atmosphere is roughly made up of 78.09 % nitrogen gas, 20.95 % oxygen gas, 0.93% argon gas, 0.04% carbon dioxide gas, and trace amounts of other gases. So the answer to this question is the one that is closest to 0.04 %, 1.