Read the passage below and decide which answer A, B, C or D fits each numbered gap.

Birds differ in their behavior just as much as their physical traits. They even use very different methods to build their nests. Some bird nests have the art of architecture beyond our imagination. Birds (21) ________ their nests in many different places and environments. Some live on high branches, some live in bushes and some of them even nest on the ground. Birds use their nests mainly to hatch their eggs and raise their (22) ________.

Because of the destruction of trees, plants, bushes, etc., these birds are losing their habitats and breeding grounds. There is a great lack of optimal breeding areas for birds. Proper breeding areas for birds are decreasing at an alarming rate. Nowadays, it is hard for birds to find even the space to build nests.

Some birds build nests on naturally formed tree hollows on ancient trees. But (23) ________, there are very less old trees left in our country except rural areas. Ducks are going towards extinction because they build their nest on old trees using the hollows, and we have almost no such trees. We know that birds play an (24) _______ and irreplaceable role in nature.

We should not destroy or harm any bird's nest. We can teach our children to observe birds and nests and how they take care of eggs. If we can encourage our children like this, it will be a great start to their education.

We need to let people know how to keep enough open space around their homes (25) ________ birds will feel safe. This is not just for the birds; it will help us too. We will gain more in the long run if we preserve the forests for our leisure and for animals and birds.