Question

carbon moves from the hydrosphere to the biosphere, and then it moves to the geosphere via limestone formation.
carbon moves from the atmosphere to the hydrosphere via gas exchange.
carbon moves from the biosphere to the geosphere via fossil fuel formation.
carbon moves from the geosphere to the atmosphere via fossil fuel combustion.
carbon moves from the atmosphere to the biosphere via photosynthesis.
step 1: a fern absorbs carbon dioxide from the air through its leaves. it uses the carbon dioxide to produce carbohydrates.
step 2: the fern dies and gets buried under layers of mud and sediment. over millions of years, heat and pressure transform the ferns remains into coal.
step 3: humans dig up the coal and burn it at an electricity - generating power plant, releasing carbon dioxide gas into the air.
step 4: carbon dioxide gas in the air dissolves into ocean water and forms carbonic acid, which breaks down

Explanation:

1. In Step 1, carbon moves from atmosphere to biosphere via photosynthesis as the fern uses carbon - dioxide for carbohydrate production.
2. In Step 2, carbon moves from biosphere to geosphere via fossil - fuel formation as the fern's remains turn into coal.
3. In Step 3, carbon moves from geosphere to atmosphere via fossil - fuel combustion as coal is burned releasing carbon - dioxide.
4. In Step 4, carbon moves from atmosphere to hydrosphere via gas exchange as carbon - dioxide dissolves in ocean water.

Answer:

Step 1: Carbon moves from the atmosphere to the biosphere via photosynthesis.
Step 2: Carbon moves from the biosphere to the geosphere via fossil fuel formation.
Step 3: Carbon moves from the geosphere to the atmosphere via fossil fuel combustion.
Step 4: Carbon moves from the atmosphere to the hydrosphere via gas exchange.