Answer:
Photosynthesis.
Explanation:
The main role of sun on the earth is the process of photosynthesis. Due to this process, life continues on earth because plants prepare their food by using this solar radiation and this food is eaten by herbivores and thus the food chain continues. If there is no sun, there is no food produced for the organisms and as a result no life occur on earth so we can conclude that sun has a big importance for the earth and its processes.