"Either the teacher or the students writes on the blackboard" is an incorrect sentence. Correct form of the sentence would be-

উত্তর জানতে একটি অপশন বেছে নাও 👇

• কBoth teacher and students on the black board, students read it.
• খWhen teacher writes on the blackboard, students read it.
• গEither the teacher or the students write on the blackboard
• ঘNeither the teacher nor the students write on the blackboard