The diagram is a model of one way that materials move across the cell membrane. Oxygen molecules are represented by two red circ
les. Carbon dioxide molecules are represented by a gray circle with two red circles attached. The left-hand side of the diagram shows the beginning concentrations of the two types of molecules. The right-hand side shows how the molecules have moved over time. A.They move to an area with a lower oxygen concentration.
B.They become transport proteins in the cell membrane.
C.They merge with the cell membrane to form vacuoles.
D.They move to an area with a higher oxygen concentration.
1 million is 1 x 10^6
1 billion is 1 x 10^9
1 trillion is 1 x 10^12
So 12 trillion miles is 12 x 10^12 which converts to 1.2 x 10^1 x 10^12 = 1.2 x 10^13
