Which of the following natural resources is most readily available to all organisms?

The most readily available natural resource to all organisms is air. Air is composed of various gases, including oxygen, nitrogen, and carbon dioxide, which are essential for the survival of living organisms. Oxygen is necessary for respiration, which provides energy to the cells of the body, while carbon dioxide is essential for photosynthesis, the process by which plants produce food. Nitrogen, although not directly used by most organisms, is essential for the formation of amino acids and nucleic acids, which are the building blocks of proteins and DNA, respectively. Therefore, air is the only option among the given choices that is most readily available to all organisms.