Hubiera Sido. Subjunctive? why?

Hubiera Sido. Subjunctive? why?
 

in my online lessons quiz this came up:
"If it had been comical, she would have recommended the movie."
"Si hubiera sido cómica habría recomendado la película."

Is "Hubiera sido" in this case the subjunctive?
why?

I've reviewed WEIRDO but cannot make this sentence fit.

It's not the subjunctive mood, but is an unreal situation. This conjugation is used with the conditional mood. AngelicaDeAlquezar answered a similar question of yours here.

It translates directly to English. If it were funny, I would have recommended the film.