"Then, she must have been at the house."

Translation: Entonces, ella debe de haber estado en casa.

[AliT.Firefly]

Where did this 'de' come from? It doesn't seem to be necessary anywhere else.

[writchie4]

"Deber de" is used to express probability. In this sentence, another translation would be something like "it is very likely that she was at home".

"Deber" (without "de") is used to show obligation. She had to have been at home (to receive a package, to let the repairman in, to make sure no rowdy kids hang out in the backyard, etc).

Take a look at this article: https://spanish.yabla.com/lesson-Deber--Deber-De-%2B-Infinitive-197

[Trillones]

Thank you.

These exercises with "deber" are making me realize that I don't thoroughly understand the proper (prescriptive) use of "must" in English, as opposed to the verbs "have to" or "should." This page about English use and conjugation (or not) or "must" shows why translating from "deber" to English and vice versa can be a little tricky -- or at least irregular.
https://www.englishpage.com/modals/must.html

[AliT.Firefly]

Thanks :)

[jeruziv]

ponele, pero en realidad, al menos en Argentina, es lo mismo. Suprimimos el “de”

[svaillenehn]

Same I thought .,

[sebastian.371]

Its missing the word "la" before casa. So, "estado en la casa"

[DABurnside]

Cut and pasted: Is it "en casa" or "en la casa"? | SpanishDict Answers
www.spanishdict.com › Q&A › Vocabulary & Grammar
According to one grammar book, it says it could be either; but "en la casa" is more common in Latin America. In another book, it says that it is always "en casa," unless "casa" is modified by a phrase to make it stand out, as in "en la casa blanca."...

[Juicy_Maffews]

Second this. Clarification anyone?

[Emily423954]

Why is "debía de haber" not also correct?

[Trillones]

I wondered this myself, and it was my first guess for this exercise. After reading Writchie4's comment about how this is most likely a sentence about probability, I now see that the verb "must" is being used in the present tense. Therefore (as I understand it), we can conjugate "deber" in the present tense.

In effect, something like, "Then [given the evidence, we conclude that] she must [present tense] have been [reference to past state, but not an active conjugated verb] in the house."

That's my stab at it, anyway.

[GarethViejoLento]

Thank you - I think that makes sense .. these obligation verbs are hard enough without tenses !

[LuSuperWhoLock]

Está incorrecto. "Debe haber estado en la casa" es correcto.

[Alice48202]

I thought one could use conditional tense to mean PROBABILITY in the past: Entonces estaria en la casa. Anyone KNOW?

[KermitRainman]

What is wrong with "Entonces, ella debería estado en la casa"?