I ____________ my homework by 9 o'clock.

To complete this sentence, you would typically use the future perfect tense, which describes an action that will have been completed by a certain point in the future. So you would say:

"I will have finished my homework by 9 o'clock."

The future perfect tense here is formed using "will have" plus the past participle of the verb "to finish," which is "finished."