Use of French

Question

I thought that using 'quoi' was impolite, verging on downright rude.  Is this no longer, or never was, the case?

Accepted Answer

Hi Isabel,
I think you are referring to the question -
Quoi? = What?
or 
Hein? = What?
wich is used to mean you don't understand something, for instance.
I was always corrected as a child, to say
 'comment?' = Pardon?
 instead.
The following snippet is from a 'bonnes manières' guide but I wouldn't go as far as using the last suggestion! :
Quand vous avez mal entendu, ne dîtes pas " QUOI ? ", ou " HEIN ? ", mais " COMMENT ? " ou " PARDON ? ", ou mieux encore " JE VOUS DEMANDE PARDON ? ".
Bonne Continuation!

Answer

If you want someone to repeat what he said, it is kind of curt and impolite in a professional and more formal setting. But as a pronoun it is, of course used in every register of the language.

Answer

I thought I should pronounce the T as in c’est un.....

Answer

Hi Lynne, 
Without context I can't answer you precisely but normally it is optional.