(In each of these examples, the auxiliary verb to have helps to form the perfect tense, which is the tense used for expressing an action's completion.)
She had been studying before the incident.
She has been studying.
She will have been studying for a month at that point.
(In each of these examples, the auxiliary verbs have and been help to form the perfect progressive tense, which is the tense used for expressing an ongoing action's completion.)
Read more about the tenses.
(In these examples, the auxiliary verb to be helps to form the passive voice. A verb is said to be in the passive voice when its subject does not perform the action of the verb but has the action done to it.)
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