French language Q&A Forum

In "le causatif", consider the sentences :

Eva s'est fait laver les cheveux par sa soeur ;

Ils se sont fait piquer par des guêpes.

I know fait is invariable here, but I don't understand why it is, and not faite or faits (or faites)

Thanks
/DO

I read the lesson and it says you use "des" for countable objects and "du, de la, de l' and des" for uncountable objects.

How do you know when to use "des" for uncountable objects instead of "du"?

Is "on" used throughout this text instead of "nous" since this is considered casual writing? 

Why are the plural "tous" and plural agreement "habillés" used with "on"? I thought it was considered a singular pronoun since it conjugates with il and elle.

this does not seem right that in the lesson it is " she takes dance lessons".. i think it should be she dances.. and if you wanted to say someone is taking dance lessons it woudl be " Elle prend des cours de danse" 

So, _____ + je = nous. If we are part of the group or speaking informally, could we use 'on' with the he/she/it conjugation instead?

Bon jour, j'habite à Chicago. Mon parents habitent à NYC. 
Où habitez-vous?
Où habitez des girafe?

Où habitent Mark Carney? Il habite à Toronto ou à Ottawa?

Bon soir,
Claire

My score was "You scored 0 out of 60 - hmm, missed your coffee this morning?!" yet it was actually my best one yet..I am not sure how to submit a ticket for this.

Is the usage of devoir for 'supposed to do something' used more frequently than censé or être censé?

Hi, I had written a question on the linked lesson but I think perhaps this is a better space. I believe I had written "à un hôpital" and this was marked incorrect in favour of "dans un hôpital."

Is this because the focus of the sentence is the work experience which takes place inside the hospital? Or what is the reason why dans can be used but not à?

Merci! 

If you're talking about a memory of a day where something happened such as "Tu te souviens du jour où personne ne pouvait la trouver ?"  wouldn't journée fit better than jour? My understanding is that journée is used when describing narratives contained within a day whereas jour is used for if you were specifically asking about the date or the point in time.