听第10段材料，回答第17至20题。

17. What is the first word the baby tried to say?

A. Truck.            B. OK.                  C. Duck.

18. How old was the baby when he learned to say that word correctly?

A. About 18 months.

B. About 21 months.

C. About 24 months.

19. What did the father do when the baby screamed that word at the airport?

A. He corrected the baby.

B. He tried to stop the baby.

C. He hid himself somewhere.

20. Why did the mother pretend not to know the baby?

A. She got angry with the father.

B. She was frightened by the noise.

C. She felt uneasy about the noisy baby.

1-5 BCAAC 6-10 CAACA 11-15 ABBAB 16-20 CABBC