1. 根据句意及首字母提示补全单词

1. （1） --I'm going to play football this Saturday. What's your p?

    --I'm going to have a piano lesson.

3. （2） The invention of Concorde was a huge s     forward in airplane history.
   

5. （3） Don't walk a        the street until the traffic stops.

7. （4） The plane will t        off in ten minutes.