Bon soir. On the video in this lesson I would like to see if I understood well.

Question

On fait que ce l'on peut.        Mange-t-on du riz. The "l" is used to avoid two vowels crashing into eachother and the "t" ??? I've seen the "t" more often than the "l". They are only for a more harmonious flow of the spoken language, but how do you know which to use when?

Accepted Answer

Hi Claudia,
In the first example -
‘On fait ce que l’on peut’ the -l is added because otherwise you would say -
‘...que on peut‘  and ‘que on’ doesn’t only clash but can sound like the rude word ‘con’ in French .
In your second example -
‘Mange -t-on du riz?
the -t is necessary as otherwise it would sound like  ‘Mange on ....’ which would sound like a command, Mangeons! ( Let’s eat!)
So, often these two letters are added to make the language flow more freely and to avoid ambiguity.
Hope this helps!

Answer

Salut My question was mainly about when do I use  L  and when I should use  T. Is there a rule or can I use them interchangeably?Merci

Answer

Hi Claudia, 
The -t is used mainly with inversion subject and verb when the verb ends in a vowel  and the pronoun starts with one , so mainly for regular verbs with ER endings but some others too -
A-t-on compris?
Achète- t- il du beurre?
A-t-elle des chances de réussir?
The -l is only with 'on' I believe, can't think of another instance where you might use it...