What is one theory that has been proposed about the formation of the universe

In many humans, exposing the skin to sunlight over prolonged periods of time results in the production of more pigment by the skin cells (tanning). this change in skin color provides evidence that -

Overtime the pond slowly becomes more acidic due to the release of chemicals from a nearby factory. which of the organisms would most likely survive the change to their environment?

Which of the following types of pollution is most responsible for large numbers of deaths worldwide because of unsafe drinking water? (a) nutrient pollution (b) thermal pollution (c) pathogen pollution (d) sediment pollution