Past Perfect Continuous

The past perfect continuous tense is used to talk about longer situations that continued up to the moment in the past we are talking about.

Past Perfect Continuous Timeline

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For example:

"By the time I left Portugal we had been living Sintra in  for five years."

"Her hand was sore because she had been playing volleyball all day long."

It is also used to say how long something went on for, up to a time in the past.

For example:

"We apologised because we had kept them waiting since lunchtime."

EXERCISES:
http://www.ego4u.com/en/cram-up/grammar/past-perfect-progressive/exercises