Fill in the blank in the following sentence with the

Solution

(1) "had rung" is in the past perfect tense, but it is not needed here because the sentence is already in past perfect. (2) "had been rung" is in the past perfect passive voice, but it is not suitable for the context of the sentence. (3) "was ringing" is in the past continuous tense, which is not the correct tense for this sentence. (4) "rang" is in the simple past tense and is the correct option for indicating the bell ringing after the completion of the paper.