Which of the following is not true about carbon? a. The total amount of the planet's carbon does not change as it moves through the spheres, because it is a closed system here on Earth.

b. Carbon is a required building block for all known forms of life.

c. Carbon is found in nearly every location on Earth.

d. It is not harmful if carbon rich gases increase in one sphere or another. It cannot change anything important as long as it stays on Earth.