D. The flow of energy,heat, and work
Normal force for the rock because that makes an object stable at its position.
static friction because micro-welts hold its particle on its position so it doesn't change in position by a potential energy. Gravity makes it stay on the ground because its force attraction between an object and the earth.
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Wood isn't as tough as rock. Wood also breaks down in weather and cracks under pressure. Plus rocks were more accessible.
Answer:
Extraneous
Explanation:
Extraneous variables are any variables that you are not intentionally studying in your experiment or test
Answer:
Obviously the answer is Sun...