Question

what is the function of the part of decomposing mushrooms that grow below the ground?
attraction of pollinators
photosynthesis with sunlight
decomposition of organic matter

Explanation:

Decomposing mushrooms are decomposers. The part below - ground helps break down organic matter. They don't perform photosynthesis (no sunlight underground) and don't attract pollinators as they are not flowering plants.

Answer:

decomposition of organic matter