The world is (a) — of uncountable natural and man (b) — objects. Natural (c) — are stone, trees, air and (d) —. Man-made objects are houses, cars, (e) — and chemicals. Natural (f) — are cyclones, earthquakes, volcanoes, storms and ocean (g) —. Life exists (h) — different conditions. It is very (i) — to keep (j) — environment clean.