Question

carbon is one of the most abundant elements in the universe. it is formed in stars and found in a variety of celestial objects, including planets. carbon is present in all of earths spheres and is an essential element for all living things.

meteor crater in winslow, arizona

scientists think most of earths carbon came from carbon - rich interstellar dust, comets, or asteroids that collided with earth billions of years ago, early in its history. today, so few carbon atoms are exchanged between earth and space that earth is considered a closed system. in other words, earth does not gain or lose a significant amount of carbon from year to year.

however, earths carbon does not remain in one place. it continually moves between earths geosphere, hydrosphere, atmosphere, and biosphere, so the amount of carbon in each sphere changes from year to year.

complete the sentences.

the total amount of earths carbon _______ significantly from year to year. the amount of carbon stored in earths atmosphere _______ each year.

changes... changes
changes... does not change
does not change... changes
does not change... does not change

Explanation:

1. For the first blank: The text says "Earth does not gain or lose a significant amount of carbon from year to year", so the total amount of Earth's carbon "does not change" significantly.
2. For the second blank: The text states "the amount of carbon in each sphere changes from year to year", and the atmosphere is one of Earth's spheres, so the amount of carbon in the atmosphere "changes" each year.

Answer:

does not change... changes