The correct answer of the given question above would be option D. The option that did not occur during the Cenozoic era is the formation of the ozone layer. The ozone layer has long been there before any era since it is part of the earth's atmosphere. Hope this answer helps.
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What is the real meaning of this questions
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Toxicity can be measured by the effect the substance has on an organism, a tissue or a cell. We know that individuals will respond differently to the same dose of a substance because of a number of factors including their gender, age and body weight. Therefore a population-level measure of toxicity is often used
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