This is _______ important book. It helped me a lot in ________ old days.

The American boy is only four years old. He can swim            the lake.

It’s reported that         medical examination （体检）will help us find out health problems as early as possible.

— __________does the baby panda weigh?   —About 20 grams.

—Oh, no! We have missed the train. What should we do?—I’m afraid we have no        but to wait for another one.