30 , составе предложения за примером,

1) They have been driving their car for two years.

2) He has been swimming for one hour.

3) She has been working for eight hours.

4) We have been using it for eighteen years.

5) He has been telling for two hours.

6) They have been playing for two hours.

7) I have been drawing for hours. (невозможно указать точное время, не указано время начала действия)