I'm watching an anime where the protagonist says, according to the subtitles, "that must be it!" But what it sounds like he's saying "あれが" instead of "あれだ". I know I may be hearing incorrectly, but is it possible for "あれが" to be said in a way that would translate to "That must be it"?
I think the only way for it to be
あれが and make sense is if it's in response to some question. Although that would be emphasizing the that in "That must be it".
- 何が一番偉いものなんだ？ → What's the best/greatest one (thing)?
- あれが！ → That one (is)! / That must be it!
If you're sure the pronunciation isn't
だ, there's a slight possibility they could be saying
や is the Kansai-ben equivalent of
だ and slightly mistakable for
が if said fast enough.