We know that trees are essential for all kinds of creatures. They give us not only food (a) — oxygen. They protect us from natural calamities. (b) — , they are called the saviour of our environment. (c) — many people are not aware of this. They cut down trees randomly. (d) —, forest lands are shrinking. (e) — people go on cutting down trees, one day there well be no trees left for us.