Over time, the cuckoo(杜鹃) has learned to get other birds to care for its babies. The cuckoo is an amazing bird.

Most birds lay their eggs and look after them until their babies hatch out(孵化). Then they feed their babies until they are ready to leave the nest.

Some birds are not such good parents. Cuckoos lay their eggs in the nests of other birds and do not care for their own babies. The cuckoo gets other birds to act as the parents. The other birds are left with the work of bringing up the young cuckoos as well as their own babies!

If the cuckoo egg hatches first, the baby cuckoo will often push the other eggs out of the nest so that it can get all the attention of its new mother. The young cuckoo sometimes even pushes the other babies out of the nest. The young cuckoo has a loud cry and is often bigger than the other baby birds. It will take all the food and the space in the nest.

A cuckoo lays around 25 eggs each year in the nests of other birds. This means that many other birds spend all their time looking after young cuckoos instead of their own babies. Some birds have learned to recognize(辨别) the cuckoos’ eggs and they push them out of their nest. But the cuckoos have also found ways of fooling the other birds. They can change their egg to make it look just like the other birds’ own eggs.

(　 ) 46．After most birds lay their eggs, they will _________.

　 A. look after them until their babies hatch out　 B. push the eggs out of the nest

　 C. eat all the eggs　 　　　　　　　　　　　　　　　　 　 D. do nothing but leave them in the nest

(　 ) 47．Over time, the cuckoo has known the art of________.

　　 A. making a wonderful nest　　　 B. getting other birds to care for its babies

　　 C. catching food quickly　　　　 D. singing songs

(　 ) 48．What do cuckoos do to their babies?

A. They lay their eggs in the nests of other birds.　 B. They do not care for their own babies.

C. They get the other birds to act as the parents.　 D. All of the above.

(　 ) 49．If the cuckoo egg hatches first, the cuckoo babies will often _________.

A. push the other eggs out of the nest　　　 B. fly to find their own parents

　　 C. help to warm the other eggs　　　　　 D. do nothing but wait for food

(　 ) 50．Which of the following statements is true?

A. cuckoo lays about 25 eggs each season in the nests of other birds.

B. No bird can recognize the cuckoo’s eggs.

C. Some birds can recognize the cuckoo’s eggs and push them out of the nest.

D. It's more difficult for cuckoos to lay eggs in the nests of other birds.