Ответ:

1. since
2. since
3. for
4. since
5. for
6. since
7. for
8. since
9. for

Объяснение:

Мы используем "for", когда действие происходит на протяжении определённого времени. Например: "На протяжении двух часов". "since" же мы используем, когда говорим о действие которое продолжалось с определённого момента. Например: "С 2001 года".

1) We've been working in the garden since we had lunch.

2) Sally has been staying with her cousin since she arrived.

3) Our friends have been travelling for tree months.

4) He's been learning Chineese since he was seven years old.

5) Have they been fishing for four hours?

6) Has Mary been cleaning the flat since two o'clock?

7) Peter has been driving a car for twenty years.

8) He's been doing karate since he was ten years old.

9) What have you been doing since last month?