Answer: A
Explanation:
Oxygen makes up another 20 to 21 percent of our atmosphere. It's essential for life on Earth, and interestingly enough, it is poisonous when highly concentrated. Our concentration of 20 to 21 percent seems just right.
Answer: It depends on if your only talking about plants if so the answer is coal.
Explanation: The reason being because coal only forms from the compaction of dead plants whereas petroleum forms from compacted plants and animals.
