Well first of all, you wouldn't ever say " al casa " because al = a el and seeing as though casa is feminine it would be "a la casa". So that should be a hint that casa wouldnt be used in this case.

Secondly there is a difference between casa and hogar. Casa literally means house where as hogar litterally means home. Although a home can be at a house, it can also be in a cave, van, street, tent or appartment etc.

a casa & a la casa were both accepted.

Most people would translate a casa and al hogar as home and a la casa as to the house. That is because a casa, like home, assumes it is your house but a la casa does not. Hogar is, of course, a word meaning home and hearth.

Are sure it was not deemed incorrect because you used "casa" rather than "hogar?"

Yes. This is what I put. However, I'm not sure of the difference in regresar and volver.

The expression "I have to/ he has to" is tengo que/ tiene que. Yo tengo volver a casa is "I have return to home"

I said "Tengo que volver a mi casa" and it was accepted!

Casa = house. Hogar = home. http://www.spanishdict.com/answers/146773/hogar-vs-casa

I'd learned in school that "a casa" meant "to home", but that never really made sense 'til now! Thanks!

Steven, "tengo que" is "I have to", and "debo" is "I must".

I don't know how exactly explain that rule, but it's the same in portuguese, "tengo" will always require "que" following it, altough the verb deber has the same meaning, this one doesn't require "que", in the cases where you are talking about obligations.

It is now "a casa". I'm not sure why it's "al hogar" and "a casa" (and not "a la casa") but I'm guessing that this is just the way it is done. I guess it could be to do with the 'h' in hogar, and that "a hogar" is not as easy to say/understand.

Out of curiosity I did a quick Google search (it's not scientific as context does not come into play) and found the following: "a casa" has 100,000,000 results, "a la casa" has 1,930,000,000 results, "a hogar" has 313,000 results and "al hogar" has 2,510,000 results. Like I say, it is not scientific, but it looks as though "a la casa" and "al hogar" are...more correct.

I agree

Hola benpdo: In this case, the phrase is "tengo que" (followed by infinitive) for "I have to" (followed by infinitive). Just think of it as one word.

i agree

That's a tricky one. In common every day expressions like go home, stay home, return home, etc, which are simply representing a location, casa without la is used to represent home. You are simply saying that the location is where you live. As on English it might not actually be a house. The Spanish word hogar is the one that embodies all those emotional connotations of home. It also means hearth. Those images of home and hearth are linked in English as well. That was a major focus of my course on D. H. Lawrence and Thomas Hardy in college, especially in Hardy's works. So saying Mi hogar es mi castillo would absolutely be more appropriate than Mi casa es mi castillo in translation of the English expression, although I don't know if it exists in Spanish or not. But all those expressions with home like to make a house a home or home is where the heart is definitely embody the sense of hogar.

Duo accepts several options and debo and tengo que are generally considered synonymous. Which answer is suggested if you make an error is somewhat dependent on what error you made. The logic is at best strange and often non existent, but it is what it is. Because you omitted the que, Duo showed you an option without the que which is debo. You are not going to find all the accepted options in the hints, and some may be incorrect in the current sentence. In English must is probably viewed as somewhat stronger than have to, although they both are about obligation of some kind. I, unfortunately, cannot speak to whether any difference in degree exists between deber and tener que. But as I said, at least on our level of linguistic sophistication, they are essentially synonymous. Duo does tend to use have to for tener que and must for deber, but that's mostly a convention for convenience of controlling the answer

That que is part of the fixed expressions tenir que to have to, and of course que will always be followed by an infinitive as in this particular expression que functions like a preposition. So your sentence Tengo que comer pasta makes sense assuming that you are trying to say I have to eat pasta. Tengo que dormir, I have to sleep. Tengo que hacer mis tareas, I have to do my homework, etc. Of course tener que is geberally resaonably synonymous to either deber or necesitar.

Did you forget the que? Tengo que is I have to, but debo does not require anything before the infinitive. Duo has a strange system for providing the correct answer if you get something wrong.

Yes, que means "to" which is distinctly different from qué meaning "what" (it took me a while to notice the distinction too).

Que also means "that" as in, for instance: Tengo que salir para que puedo llegar a tiempo ("I have to leave so that I can arrive on time")

Well that's a somewhat complex question. Que can be a subordinating conjugations and may separate two verbs in two clauses. But when you see two verbs together like this with the second verb in the infinitive you sometimes have no preposition at all, as with all modal verbs and some others, or you have a preposition. The most common ones are a, de and que, I would think that is listing the order in terms of frequency of use. It is the first verb which determines which preposition to use. In a few cases different preposition will work, and often there are set combinations for different expressions. Tener que (infinitive) is a set expression for to have to (perform the verb).

Here is a link listing some of the common verb phrases with prepositions. You will see that que is not really particularly common in this function beyond to have to.

http://www.peppyburro.com/blog/spanish-verbal-phrases-infinitive/

I know what you are saying, but the trick is actually not pay too much attention to the English translation for prepositions. You just have to learn the preposition that goes with the verb or expression by rote. They will sometimes make consistent sense, and sometimes not. But that's pretty much the nature of prepositions. Try justifying the various prepositions to à foreigner for variations like stand up, stand down, stand in, stand out, stand to, stand for, stand about, stand of,

It would have to be Tengo que volver AL hogar. This usage here is sort of unique to casa. With the la it means return to the house, without la it means return home. But for the most part you will have the definite article and the noun. Volver a la escuela, volver al aeropuerto, etc. Of course you won't have the definite article before Cities, counties,, etc. But otherwise you should. But I am not certain that Duo will accept it. They can get a little myopic when the answer they want to teach is a different option from the most literal.