Which of the following is the most accurate description of gravity?

a. objects fall unless they are supported.
b. forces that keep us on the ground and from floating into outer space.
c. a natural force of attraction exerted by the earth upon onjects that pulls the objects towards earth's center.
d. any force that pulls one object into another object.

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.