Question

where does most of earths available carbon come from?
a the constant process of photosynthesis
b. sunlight that is transferred from the sun to earth
c. the convection process that occurs in earths mantle
d. dead organisms that are recycled back into the environment

Explanation:

Photosynthesis takes in carbon - dioxide, sunlight provides energy not carbon, and mantle convection is not a major source of available carbon. Dead organisms contain carbon which is recycled back into the environment through decomposition and other processes, contributing to most of Earth's available carbon.

Answer:

D. dead organisms that are recycled back into the environment