65A, consisting of the auxiliary may+the base have, +B, consisting of the auxiliary have+the -ed participle been, +D, consisting of the auxiliary ie+thc -edparticiple examined, where have is shared byA and B and be(eri) is shared by B and D.The order in which the four types can form combinations is indicated by thealphabetical symbols (A, B, C, D) which label them.