Answer:
This question lacks options, however, it can be answered based in general understanding. The answer is:
The carbon is released into the atmosphere and soil during decomposition
Explanation:
Carbon is an important element that makes up the biomass of living organisms. Organisms like plants as described in this question, store carbon as sugars, which they synthesized during photosynthesis. However, when they decompose/decay, they lose this carbon content.
Decomposition is the process carried out by microbes such as fungi, bacteria etc involving the breaking down of an organic molecule into inorganic ones. Hence, when leaves of a plant die, they undergo decomposition i.e. the carbon content in their leaves present as sugar (organic molecules) is broken down to release the carbon in form of carbon dioxide, into the atmosphere, soil etc. Hence, the carbon that is stored in leaves are RELEASED when they decay causing them to lose mass.
