What have the scientific studies identified as the major cause of acid rain in the united states?
volcanic ash in the air
burning of fossil fuels that release sulfur and nitrogen compounds into the air
excess solar radiation due to the depletion of the ozone layer
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chemicals still in the atmosphere from the asteroid collision with the earth

What are four key elements of the study of economics?

The image shows the evolution of a species of fish. a few fish from a population developed different social behaviors and evolved into different species. two fish according to the image, the fish underwent . the new species of fish had mating seasons that were different from that of the original fish. because of the differences in mating seasons, the fish underwent reproductive isolation. this mode of isolation would be .

The function of the excretory system is to control homeostasis and