In general, molecules move across the plasma membrane readily, while molecules need special transport systems to move them across the membrane.

Which of the following statements is a scientific claim? a. the early solar system had large amounts of water; so, the oldest objects in the solar system should also be abundant in water. b. earth is shaped like a sphere even if not all of the scientific observations related to its shape support this idea. c. the mass of the universe is much greater than current models predict; it is not possible to explain this inconsistency. d. planet earth is abundant in water, but there is no way to scientifically determine from where earth's water originated.