Which of the following tenses is used to show an action that is completed before a certain point in the future?

The tense that indicates an action completed before a certain point in the future is the Future Perfect tense. This tense is formed by using "will have" followed by the past participle of the main verb. It expresses the idea that an action will be finished before a specific moment or another action occurs in the future.

For instance, in the sentence "By next year, I will have graduated," the graduation is an action that will be completed before the point of "next year." This shows a clear distinction between something that is completed and a future time reference.

The other tenses listed do not fit this definition as effectively. The Future tense simply indicates actions that will take place in the future, without the completed aspect. The Simple Present tense describes habitual actions or general truths rather than actions in the future. The Past tense conveys actions that have already been completed but does not relate to future actions in the way the Future Perfect does. Thus, Future Perfect is the only tense that aligns with the requirement in the question.