Fill in the blanks with the most appropriate option:-

The students __________ not interested in the lesson because it was boring.

were

The correct option to fill in the blanks is were.

The sentence "The students were not interested in the lesson because it was boring" is in the past tense, and it is referring to a state of being in the past. The other options are not as appropriate.

• Have is the present perfect tense of the verb "to have". This does not make sense in the context of the sentence, as the students are not currently not interested in the lesson, but they were not interested in the lesson in the past.
• Are is the present tense of the verb "to be". This does not make sense in the context of the sentence, as the students are not currently not interested in the lesson, but they were not interested in the lesson in the past.
• Can is the modal verb "to be able to". This does not make sense in the context of the sentence, as the students are not not interested in the lesson because they are not able to be interested in it.