16. FALSE
17. TRUE
18. FALSE
19. TRUE
20. TRUE
Answer:

The air in the atmosphere consists of nitrogen, oxygen, which is the life-sustaining substance for animals and humans, carbon dioxide, water vapour and small amounts of other elements (argon, neon, etc.). Higher in the atmosphere air also contains ozone, helium and hydrogen.
Answer:
The amount/type of stain
Explanation:
You would want to ensure that the stain was the same in both samples.
Answer:
First of all, it's KNO₃ not KNO.
Second, KNO₃ is neither an acid nor it is a base, infact, it is a salt and therefore it's neutral.
hope that helps...
Female energy the answer is the first one