Still confused about past tenses!

Still confused about past tenses!
 

How do you say "What was that?!" when something occurred just a second ago, for example, when something just flew past your head. Is it "qué era eso?" "qué fue eso?" or "qué ha sido eso?" ???

¿Qué fue (eso)?

Thanks for the reply, Rusty, but I'm still unclear as to why?

I know that in Spain, for example, they say "Qué has dicho?" when they didn't understand what you just said to them a moment ago. Why is the past tense different for this one then? Because it also deals with something that happened just a moment ago.

There is a regional difference. In Spain and other few countries, we use the "pretérito perfecto" (¿qué ha sido eso?) for an inmediate action/fact. However, native Spanish speakers from most countries prefer to utilize just "pretérito" in the same way native English spakers do in USA.

A pleasure.

It's like English in this case. What did you just say? What have you just said?
There's a slight meaning change but often can be interchanged.