Answer: C. 30 - 50 million years ago
Explanation:
Fossils found in layer Y formed 30 million years ago according to the graph above. Similarly, fossils found in layer Z formed 50 million years ago.
If a fossil (fern fossil) is found between layer Y and layer Z, it means that it formed between the years that the fossils in layers Y and Z formed which is 30 - 50 million years ago.
"Exponential growth" means that the bigger it is, the faster it grows.
That's Choice 'D'.
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Answer:
One could be in the cell. The cell respires, thus producing carbon dioxide in it. So the concentration builds up in the cell. Diffusion is the net movement of particles from a region of high concentration to a region of low concentration, and the carbon dioxide concentration outside the cell is less, therefore the carbon dioxide molecules moves outs of the cell.
Another scenario is when perfume is sprayed into the air. The perfume particles collides with the air particles (lower or no concentration of perfume). This process goes on and on. This is diffusion since the concentration perfume particles collides with the less concentrated particles of perfume.
Probably if there are not enough plants in that area
