Answer:
B. an adjective.
Explanation:
The possessive form of the noun teacher is teacher's. This is called the genitive case. This case is used to modify nouns and it is used to indicate possession. For example: The teacher's lessons are interesting. The possessive form of teacher or the genitive case is indicating we are referring to his / her lessons as opposed to, for example, the Head's lessons. The School Head might also teach and we can compare both lessons: the teacher's lessons and the head's lessons.
