In the given sentence, the verb 'were interrupted' suggests that the sentence is in the past tense. Further, 'interrupted' indicates that the doer's action was going on and was left incomplete. Thus, the answer must be in the past continuous tense.
Option A is incorrect. 'have told' is in the past perfect tense. Thus, it indicates that the action had been completed and is the incorrect answer.
Option B is correct. 'were telling' is in the past continuous tense and indicates that the doer's action was incomplete and continuous. Thus, the answer is correct.
Option C is incorrect. 'told' is in the simple past tense. Thus, it indicates that the action had been completed and is the incorrect answer.
Option D is incorrect. 'are telling' is in the present continuous tense. Using it will make the tense of the sentence inconsistent. Thus, it is grammatically incorrect.