French language Q&A Forum

I use Word Reference as my bilingual dictionary.  Here's their note on the two spellings.  Note: "ass(e)oir" and "rass(e)oir" have two conjugations. The conjugated forms with an "e" are more common than those with an "o". 

I wrote 'les chauves-souris' . Your text was 'les chauve-souris'. After completion of the dictee, I checked dictionaries which add s to chauve in the plural form. ??

I can use the word(  professeur) as masculine and feminine.

It was marked wrong and shown as the wrong answer. So my score went down.

As it is the girl who says that she is sure, shouldn't it be "Je suis sûre que ... " instead of "Je suis sûr que ... ? 

Also, is "Ce n'est pas grave" (with silent "ne") an accepted alternative for "C'est pas grave" in writing dictation? (I often can't hear all the little words in spoken French but still try to include them in my written responses)

Bonjour Madame !

I have carefully read the green box which states that when y pronoun comes after ER verbs in tu form in L’Impératif , then the dropped-out s is recovered.

But for the verbs like ouvrir, couvrir , offrir , découvrir which though are “IR” verbs but are conjugated like  “ER” verbs , will this case persist for them also ?

If so please provide a few examples to illustrate the same.

Bonne journée !