Over the past 60 years, the level of carbon dioxide in the atmosphere has been continually increasing. many scientists hypothesize that this increase has led to an imbalance in the carbon cycle and a climatic trend known as global warming.

in which of the following ways could humans the carbon cycle return to normal?

a.)reduce the amount of fossil fuels they combust
b.)cap volcanoes so that they do not release more carbon dioxide
c.)pump nitrogen and oxygen into the air to rebalance the atmosphere
d.)cut down trees and other large plants that depend on carbon dioxide

Read this summary of a scientific theory: "cells are the most basic structural and functional units of life. all living organisms are made up of one or more cells. all cells that are alive in the world today came from pre-existing cells." which of the following would require this theory to be modified? -a.) a survey finds that a majority of people believe viruses carry out the basic processes of life. -b.) a prominent scientist says she feels strongly that one day the theory will be challenged by life on other planets. -c.) the dna of unicellular and multi-cellular organisms is shown to have many fundamental similarities. -d.) scientific observations show that microscopic organisms living in the deep ocean are not made up of cells.