The people use Earth's motion to determine units of time because of its uniform motion which is consistent.
<u>Explanation:</u>
In earlier days, people used to observe the motion of Earth to measure time. This is because, the Earth is moving at constant speed and at constant acceleration. So the change in position of the sun or stars can be easily correlated to the time.
Due to the consistency in the Earth's motion and the accurate repetition of the time period along with the seasons, the Earth's motion can be considered as a responsible source to determine the units of time.
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1) 100s of millions of years ago Trees and plants fall into swamps
2) Layers of rotting plant matter builds up underwater
3) Over millions of years the weight of layers heat the plant matter and turn into Peat
4) Over millions of years more pressure and heat turns Peat into coal
statement c would be correct I think.
