The main organic source of energy for living things is

The Sun

Explanation:

Nearly everything eats sunshine – or eats something else that ate sunshine. The Sun is the major source of energy for organisms and the ecosystems of which they are a part. Producers, such as plants and algae, use energy from sunlight to make food energy by combining carbon dioxide and water to form organic matter.

answer; the correct answer is desert plants;

stress fractures occur largely in the feet and legs and are common in sports that require repetitive impact, primarily running/jumping sports such as gymnastics or track and field.