Recall the chemical reaction of photosynthesis: 6CO2 + 6H20 - C6H12O6 + 602. Why are forests referred to as "carbon sinks"?

Because they absorb and store more carbon in form of CO2 during photosynthesis than they release

Explanation:

A "sink" as opposed to source is a site where something is deposited or stored rather than produced. Plants in the forest vegetation are capable of a unique process called photosynthesis, in which they manufacture their food using inorganic carbon as powered by light energy. The photosynthetic equation is given below;

6CO2 + 6H20 → C6H12O6 + 602

Based on the equation above, carbon dioxide is required for photosynthesis and is obtained from the atmosphere via the stomata on the leaves. This means that carbon in form of CO2 must be stored in the plant prior to photosynthesis, hence, FOREST is referred to as CARBON SINKS because it absorbs and stores more carbon (CO2) during photosynthesis than it gives out.

"d.) carbon dioxide and hydrogen sulfide"