1. She (has/had been sitting) at the window since 10 o'clock. (оба варианта применимы, т. к. нет привязки ко времени)
2. He will (be training) from 6 till 8 o'clock next Friday.
3. I didn't speak to him because he (was making) expirement.
4. Now they are ( deciding) where to go for the Holyday this summer.
5. By 5 o'clock the device (had been operating) for 3 hours and didn't stop.
6. I'd like to know what (has) happened to him. (оба варианта применимы) 7. By this time tomorrow the train will (have left)