You could imagine sentence (a) (being??) uttered by someone consulting their diary and seeing that tomorrow's page is blank.
I can imagine him (being??) really angry.
I can't imagine elephants (being??) able to fly.
https://dictionary.cambridge.org/dictionary/english/imagine says the verb "imagine" is sometimes followed by the ing-form of another verb: She imagined herself sitting in her favourite chair back home. So my question is: do we need "being" in (1) (using the passive voice), (2) and (3) (both using an adjective)?