Past Perfect Continuous Tense

We were waiting for a bus for half an hour

We had been waiting for a bus for half an hour

We been waiting for a bus since half an hour

We had been waiting for a bus since half an hour

'd been working

was working

had been working

had worked

When I came into the classroom, the students were discussing a plan of the excursion. They were discussing it for 20 min.

When I came into the classroom, the students were discussing a plan of the excursion. They already discussed it for 20 min.

When I came into the classroom, the students were discussing a plan of the excursion. They had already been discussing it for 20 min.

When I came into the classroom, the students had discussed a plan of the excursion. They had already been discussing it for 20 min.

The boys said they had been rowing for a long time

The boys said they were rowing for a long time

The boys said that they have been rowing for a long time

The boys said that they had been rowing for a long time

Were you searching for a room for two hours before we had found a free one?

Had you been searching for a room for two hours before we found a free one?

Did you search for a room for two hours before we found a free one?

Have you been searching for a room for two hours before we found a free one?

had known/were playing

knew/were playing

knew/had been playing

had known/had played

had known

had been knowing

have known

knew

for all day

during the day

since the day

all day

He had been watching TV.

He hadn't been watching TV

He was watching TV

He watched TV

He was running

He ran

He has been running

He had been running