Prove that mosses are capable of photosynthesis? why do they need this process?

Mosses are capable of photosynthesis. Chloroplasts prove this, but photosynthesis itself is slow. But photosynthesis is capable of taking place even under a layer of snow, which is why mosses remain green even in winter.
Mosses need photosynthesis, otherwise they will not be able to form organic substances from organic substances.

One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.