"I walk in the morning."
Translation:Je marche le matin.
Thanks Sitesurf, the difference is rather clear, at least for me, but it still doesn't hit the point because the English sentence doesn't exclude any of the options you wrote about. If there would be "au travail", "marcher" would fit much better. Without the purpose of the morning walk all the meanings should be equally accepted.
So many of the problems in Duolingo result from the fact that they give short phrases to translate, rather than complete sentences. That's ok IF the short phrases aren't ambiguous -- but many of them are too short and have different shades of meaning. We shouldn't be left to guess their meaning. I love the program (best one I've found online) but it could be improved enormously if they focused more on meaningful, unambiguous sentences and deleted the short, ambiguous phrases.
This is an article on French temporal prepositions which may help you: http://french.about.com/library/weekly/aa040100.htm
I do appreciate your reply, but it still doesn't make sense to me when Google translate tells me 'Je marche du matin' and my French college teacher says the same. Duolingo didn't say 'from morning to evening'. Am I missing some context that your answer didn't explain? Thanks. :)
"marcher" has 2 distinct meanings: to walk (j'ai marché jusqu'à la gare/I walked to the station) and to work (la machine marche bien/the machine works well).
"Faire une promenade" is to walk idly, for pleasure.
If you mean that you go somewhere "on foot", you will use "aller à pied", rather than "marcher".
There is no strict rule when it comes to translate "in" to "en" or "dans".
Directionally, "dans" is more concrete and "en" reserved for specific uses like years and months and some places.
"in the morning" = "le matin" (as a habit and date); "dans la matinée" (in the course of the morning as a duration)