Past Perfect Continuous

Past Perfect Continuous
action continuing a period up to a spe¬cific time in the
 She had been working as a clerk for 10 years before she resigned.
past action of certain duration which had visible results in the past.
 They were wet because they had been wolking in the rain.
the Past Perfect Cont. is the past equivalent of the Present Perfect Continuous
 (She is going to the doctor. Her leg has bem aching for two days.) She went to the doctor. Her leg had been aching for two days.