Past Perfect Continuous
had + been +
Ving
for
since
Действие
1) длилось
2)
до определенного момента в прошлом
3)
в течение какого-то времени /с какого-то времени
By the time mother came, Tim had been doing his
homework for an hour.
Nelly was tired because she had been working in the
garden since early morning.
