select the most appropriate option to fill in each blank.

The issue of growing environmental pollution should be considered as one of (1) ______ importance. The environment (2) ______ the air we breathe, the water we drink, the trees and plants that (3) ______ food for us and the animal kingdom. All of these together form the circle of life on earth. Pollution is a process by which natural elements of the earth are negatively (4) ______, causing harm and (5) ______ to this circle of life.