I believe the answer is a. crossing over
<h2>Answer</h2>
Fossils are often found in <u>Sedimentary</u><u> </u><u>rocks</u> because it is formed from the remains of once living things.
<h3>#CarryOnLearning</h3>

natural selection light water and carbon dioxide
Balancing, running, and jumping are all examples of <em>gross</em> motor skills.
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I quote from Wikipedia:
"Gross motor skills are the abilities usually acquired during childhood as part of a child's motor learning. By the time they reach two years of age, almost all children are able to stand up, walk, jump, run, walk up stairs, etc. etc."