When did the phanerozoic eon begin? about 10.1 million years ago about 2.0 million years ago about 540 million years ago about 20.5 billion years ago

Option C, About 540 million years ago

Explanation:

The Phanerozoic Eon  started from the end of Precambrian period and consists of three eras namely Paleozoic Era , the Mesozoic Era , and the  Cenozoic Era. It also consists of 12 geologic period. The Phanerozoic Eon is still continuing till today since it started some 540 -570 million years ago. It is this period which marks the evolution of complex lifeforms such as invertebrates ,some 500 million years ago.

Thus, option C is the appropriate answer.

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sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.