Concept:Air is the natural resource always present around all organisms without any effort.
Explanation:All living organisms are continuously surrounded by air.
Air contains essential gases, such as oxygen and carbon dioxide, which are needed for life.
Oil, water, and food are not readily available in every habitat without effort.
Air, however, is found almost everywhere organisms live.
Therefore, air is the most readily available natural resource to all organisms.
Answer:C. Air