Verbs: Conditional Perfect
O que teria acontecido?
Use teria plus the ‑do form of a verb to talk about things that would or could have happened.
Ela teria adorado este filme.
She would have loved this movie.
O que teria acontecido com elas?
What could have happened to them?
O que ela teria feito?
Don't forget that the ‑do forms for ter, fazer, and dizer are special!
Eu teria tido uma doença.
I would have had a disease.
Ela não teria feito isso.
She would not have done that.
Eu teria dito a verdade.
I would have told the truth.
O que teria havido?
The verb haver means to happen. You can use it with teria to talk about things that have supposedly happened.
Teria havido algo.
Something must have happened. (Literal: There would have been something.)
Note that there's no person like eu or você in Teria havido algo. And you can use teria havido even with plural words (like problemas) without changing a bit!
Teria havido problemas.
There would have been problems.