Select the option which fits appropriately in the blank:I work as _ only English teacher at this school.

Explanation

I work as the only English teacher at this school.The definite article "the" is used before "only English teacher" because it refers to a specific position or role that is unique within the context of this school. It specifies that among all the teachers at the school, there is only one English teacher, and that is the role the speaker holds.