"by bus," "on the bus," "in a bus"... There are lots of ways to say this. How do we know in advance which one they choose as a translation? They often translate it in exact and awkward English, so it's hard to know whether to be exact or choose some variation. I wish they would fill us in on the "accepted" translation before they quiz us on them.
This is a program and they can only predict how people may translate it. There are often a number of correct ways in which any of the sentences can be translated. This is not a test, so if you feel a translation should be accepted, report it. Once you do that DL has already provided the answer they are looking for, so learn from it and enter the sentence as DL suggested when they said wrong answer. Keeping in mind that your answer might not be wrong, just not acceptable at this time. If we don't know the exact acceptable answer(s) then DL provides them. And yes I sometimes roll my eyes over how DL phrases a sentence....have a good chuckle, suggest to DL a better way then move on and enjoy.
I know that "I always take the bus to work" wasn't the exact translation, but I would find it very awkward to say, "I always go to work by bus." Normally, I agree with exact translations, but when a sentence ends up sounding awkward in English, I'd rather Duolingo accept an inexact translation that's more natural to the native language. Perhaps it's just me, though, who feels like Duolingo's translation sounds awkward--regional differences and such.
Although if a foreign speaker were to use the expressions you use above, an English teacher would correct them. It is common usage to say "I always go to work by bus"; similarly with "I go to work by car" or "I drive to work". Would you really say "I always go to work in a train" or "I always go to work in the tube?" (Genuine question, I'm curious). It's a question of nuance; the use of "by" makes it clear that that you're getting somewhere via the vehicle in question and that the vehicle itself is not your final destination or place of work. It's a similar distinction to the Spanish use of "por" versus "para" and "en" although Spanish is certainly more rigid regarding the usage.
Certainly it makes it clearer using "by", though if someone asked me "how do you get to work?" and I answered "In a car." there would be no ambiguity because the question is about how you get there. It's one of those little things you never really think about when you say it, I probably have used both in sentences when asked, but again it's not a question I get asked a lot if ever. But I will concede that the correct usage for clarity should be "by" and for English learners it's important to get it right, us native speakers can butcher the language all we want ;-)
We do, we really do! But that's because we can. What I mean by that is that one of the wonderful things about the English language is how fluid it is. Also, someone's meaning or intended meaning can still largely be understood even if words are completely misused or placed entirely in the wrong order...in many languages, incorrect syntax will literally render a sentence meaningless. One of the things I love about learning a foreign language is how much it makes me think about my own.
Because "Trabajo" is one of the Spanish nouns that need a definite article before it when used after "a".
There are a number of such nouns, mostly related to locations, that need a definite article.
Clase Colegio Cárcel Lo llevaron a la cárcel. Iglesia Casi nunca voy a la iglesia. Universidad Hospital Mi amigo está en el hospital. Cama Me fui a al cama temprano. Cine Camomento (I believe) Prisión
See these references: http://aprendeinglessila.com/2014/03/articulo-determinado-the/# https://www.hablamejoringles.com/articulo-sobre-articulos-el-uso-de-the-en-ingles/ http://www1.udel.edu/leipzig/Assistant/artdef.htm
Incidentally, meals and food also need the definite article before them.