What is the el/ella/Ud, form of estar?

Pongo i put la carta dentro de uno de estos

Which one of the following is the correct rhyme to keep in mind when using the spanish counterparts to this, that, those and these? a “this” and “these” both have t’s, “that” and “those” don’tb “that” and “those” both have t’s, “this” and “these” don’tc “that” and “those” both have s’s, “this” and “these” don’td “this” and “these” both have s’s, “that” and “those” don’t

The imperfect verb that matches the given pronoun. he / she / you