Question

13. In which sphere does carbon build up for millions of years in the form of coal?

a. Atmosphere
b. Mega sphere
c. Hydrosphere
d. Geosphere

Answer 1

d. Geosphere

the carbon enters the geosphere (Earth) through the biosphere by means of decaying dead organic plant and animal materials undergoing fossilization there by becoming incorporated in organic rich oil and gas (fossil fuels)

Answer 2

C. Hydrosphere

Reason I did this already