1. Mammals seldom live in the trees.
2. Boxes are often made of cardboard.
3. One can hardly see this wonderfull bird. It has become almost extinct.
4. Usually you can find the most interesting species of animals in zoological gardens.
5. When people from time to time ruin natural habitats, birds and animals always leave them.
6. We often say "birds and animals" forgetting that birds are also animals.
7. Sometimes it is difficult to cure this disease.
8. In this part of the country it hardly rains in summer.
9. People seldom keep reptiles as pets.
10. From time to time you can see swans on the ponds in our cities.