I m trying to figure out what this sentence is and the Passive Past Perfect Continuous Interrogative is the best that I can think of Where have all the reference books been put It has the have been present part form of the Past Perfect Continuous Would have and been be considered auxiliary here...
ESL General English Grammar Questions
by
naylorm
16 days ago
Grammar, Verbs, Constructions, Tenses, Auxiliaries, Past Perfect, Past Tenses, Determiners, Sentences, References, Business, Career, Animals