Noah wants to show the largest source of carbon on earth for his school project. according to his research, in which form is most of the carbon on earth stored?

I'm not sure what they exactly mean by "form" but,

Most carbon is stored in the ocean in sediments. These sediments and rocks develop from the hard shells and body parts of marine organisms that have absorbed the carbon in the water. When they die, their bodies sink to the ocean floor, and the hard parts break down into sediment, which later are formed into sedimentary rocks.

When in contact with water that is acidic carbon dissolves and will precipitate out as sediment such as calcium carbonate (limestone). This cycling between solution and precipitation is the background against which more rapid parts of the cycle occur.

So, it should be sediments, but it could also be calcium carbonate..

The majority of carbon is present in the dissolved state in the ocean and in the limestone rocks on the ocean floor.

Explanation:

Carbon is one of the main greenhouse gas that is emitted mainly from the volcanic eruptions and burning of fossil fuels. Some amount is released by the living organisms during respiration.

This carbon is then transported from the atmosphere to the lithosphere through the rainfall (precipitation). This atmospheric carbon when reacts with the water, it forms a weak acid which is commonly known as Carbonic acid. This acid-containing water reacts with water undergoing chemical weathering releasing ions such as, calcium, magnesium, sodium, which are further carried bu the rivers to the oceans.

These calcium ions then react with bicarbonate ions, thereby forming calcium carbonate. In addition to this, they are also formed by organisms that are comprised of hard shells. These organisms when they die, they sink and accumulate at the bottom of the ocean floor. With the increase in time, these shell layers combine with sediments forming carbonate rock called limestone in which the carbon is stored.

the answer is b. glad to .