Question

what are the sustaining present on earth?

Answer 1

For life as we know it,carbon,oxygen and nitrogen are vital and sometimes sulfur.other life forms may have adapted and use of silicon instead of carbon,or may be they are metal based.

Answer 2

Water and Oxygen are the main reasons we are living on this earth. Besides these carbon dioxide, hydrogen, sulphur, nitrogen, zinc, iron and suitable climate made life possible on earth.