To be able to compare the results to a sample without any of the independent variable added.
The answer is Sold radiation
Fossils can give information about past environmental conditions by showing the type of animal they belonged to. If a scientist found a whale fossil in a desert, he/she could assume that the desert was once an ocean as whales only live in oceans. If someone found a fossil of a lizard that inhabited trees, in the middle of the ocean, then he/she could assume that the ocean didn't exist at one point and instead, there might have been a forest in it's place.
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(D), amount of time and area of physical contact between the substances
Viruses are classified as non-living. Although they have DNA or RNA as genetic information, a protein coat, and some, a lipidic envelope, they do not have the machinery to multiply on their own and therefore are non-living. <span>A </span>virus<span> is simply an </span>infectious agent<span> that, through different ways, many times only by releasing its genetic information inside the cell, </span>replicates<span> using other living-cells machinery</span><span>. Viruses are able to infect any type of cell.</span>
