Answer:
Most of the time grammar comes after 'common sense" which is inevitable. Grammar rules don't matter anymore when it comes to informal conversation. We only pinpoint grammar errors when we don't understand the statement. So the easiest way to know if the sentence makes sense is to check if in all time subject agrees to its predicate or supporting details.
Explanation:
Pon el texto para ayudarte
¿Tú subiste por la escalera o en el ascensor?
Why subiste?
Subeste, nope, nope, no, this isn't a word in Spanish. This is how we know this one is wrong.
Subaste? Not a word either. This is crossed out.
Subes, This is a word but it's stating something instead of asking a question. "Tú subes por las escaleras = You climb/ go up the stairs".
So subiste is the right one!
Hope this helps!~
