The correct answer is C. flew.
Kites are inanimate objects, so they cannot fly by themselves. They must be flown by someone. The past tense of “fly” is “flew.” Therefore, the sentence “Kites flew last year also” is grammatically correct.
The other options are incorrect because they do not agree with the subject of the sentence. “Did fly” is in the past tense, but the subject of the sentence is “kites,” which is plural. The past tense of “fly” for plural subjects is “flew.” “Were flown” is also in the past tense, but it is in the passive voice. The passive voice is used when the focus of the sentence is on the action, not on the person or thing doing the action. In this case, the focus of the sentence is on the kites, not on the person or thing flying them. “Flying” is the present participle of “fly.” The present participle is used to form the present progressive tense and the perfect tenses. In this case, the present progressive tense would be used to describe an action that is happening right now, and the perfect tenses would be used to describe an action that has already happened or will happen in the future. Since the sentence is about something that happened in the past, the present participle is not the correct verb tense.