Est-ce que c'est le cahier professeur de math?
oui, c'est le cahier de monsieur lebrun.
a. du
b. de la
c. des
d. de l'

The answer is A.
It cannot be 'de la' since the teacher is male.
It cannot be 'des' since there is not more than one teacher.
It cannot be 'de l'' since the word 'professeur' does it start with a vowel.

Omg it is so much but i think it will be b