Bonjour
So you have to learn "quel" and "lequel".. interrogative pronouns which agrees in number & gender with the following noun ...
quel, quelle, quels, quelles = which
lequel, laquelle, lesquels, lesquelles = which one
J'ai plusieurs craies. (which one) Laquelle veux-tu ?
Tu as vu cette voiture ? Non. (Which) Quelle voiture ?
De (which) quelles photos parles-tu? (une photo , des photos =short name for photographie = feminine noun)
Quel bananes as-tu mangées ? INCORRECT ==> quelles + noun fem.plural (bananes)
Quels animaux sont les plus petits ? CORRECT => quels + noun masc. plur. (animaux)
Est-ce que tu as vu ma nouvelle robe ? (did you see my new dress ? No, which one ?)
Non, laquelle ?
laquelle = which one = refers to a dress= noun fem sing. so it has to agree with the following noun which is fem. sing.
Quel est ton nom = CORRECT =What is your name ? (nom is masc. sing. soyou have to use "quel"......... [which is your nationality? Quelle est ta nationalité ? = (une) nationalité = fem noun --> quelle]
Voilà deux jupes. Laquelle préféres-tu ? CORRECT
Here are two skirts ? Which one do you prefer ?
so let me try to explain-------------------------------------------------------------------------- you know that 'which one' = lequel, laquelle, lesquels, lesquelles ......it all depends on the following name...........you have to agree the pronoun with it .. a skirt = une jupe => fem. sing. ==> laquelle
the correct form of quel ??????????????????????????????????????
------------étudiant a étudié pour l'examen?
étudiant = masc. sing.noun ==> quel (pronoun masc. sing.)
Quel étudiant a étudié pour l'examen ?
Lequelle des deux filles est la plus belle ?
Now that I tried to explain that "quel, quelle, quels,quelles" or "lequel, laquelle, lesquels,lesquelles" agree with the following noun...........................
filles = fem. plural; but you're asked "which one of the 2 girls" ?-->= "laquelle"
===> laquelle des deux filles est la plus petite ?
J'ai perdu mon livre. OH zut ! lequel ? (refers to the book..= which one + masc. noun) ====> Oh zut ! lequel ?
As-tu vu mes lunettes ? (fem. plural) Non, lesquelles (fem. plural)
À --- nombres penses-tu ? (nombres = masc. plural ==> quels)
À quels nombres penses-tu ?
Ok.. I tried to explain.. but I'm not a teacher..!! Hope I helped :)