Which treatment is physical and is used to remove solids from the
wastewater?
O primary
O secondary
O tertiary

List two limitations of natural selection

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

Which of the organisms listed below performs nitrogen fixation? a. legumes b. plants c. bacteria d. fungi