English Grammar-Past Perfect Continuous Tense

Structure of sentence: Main verb: Present participle (‘ing’) Eg: going, playing, reading etc. Auxiliary verb: Had been (whatever may be the subject). The formula for past perfect continuous tense (Positive) is: Subject+Auxiliary verbs+Main verb(ing form). Positive          Negative                 Interrogative I had been writing. I had not been writing. Had I been writing? We had been writing. We had not been...