I believe the answer is B.
when an animal dies and its body decays, it can leave an imprint in the sediment. If this imprint fills in with minerals from sediment and groundwater, it can harden to form a fossil. This fossil is called a cast fossil. The fossilized imprint is called a mold fossil.
Air is a homogeneous mixture mixture of several gases
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Ice has a lower density than water or any other liquid, which allows it to float.