The correct answer choice which is not a hypothesis stated in the text for why the Cambrian explosion occurred is :
Oxygen levels reached a level that allowed animals to be more efficient at using aerobic metabolism
A hypothesis can simply be defined as a verified reasonable explanation for a particular naturally phenomena
So therefore, the correct answer choice which is not a hypothesis stated in the text for why the Cambrian explosion occurred is :
Oxygen levels reached a level that allowed animals to be more efficient at using aerobic metabolism
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