Why was 1990 an important year regarding air quality? Check all that apply.
2.Cost-effective ways to reduce pollution were emphasized.
4.Modifications and improvements were made to the Clean Air Act.
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The answer for the first question is A. Proton is the subatomic particles which adds most of the mass of an atom as well as the neutron since they have the same mass. Photon, on the other hand, is not one of the subatomic particles.
Answer:

Explanation:
Iron is Fe, nitrogen is N. Nitrogen is diatomic, which means it occurs as a molecular pair by itself. Iron III nitride has a chemical formula of FeN because nitrogen has a charge of 3-, and iron III tells us the iron has a charge of 3+ so you just need one of each to make the charges balance and the compound neutral.
Answer:
A
Explanation:
Your answer would be A because Earth is formed from cold gases collapsing due to gravity. The Solar System was formed when a huge amount of dust and gas began to collapse under its own gravity, and as the cloud collapse it started to spin causing the material within the cloud to gather into a swirl and then formed into planets and as the planets are formed they kept this spinning motion.