<span>Lillian will have been talking for two hours by the time she finishes her classical music lecture.
Let's assume that the underlined verb is "will have been talking." The underlined verb is in the tense of future perfect progressive. Because of the word will, it gives us the clue that it is future. Because of the line have been talking will give us the clue that it is perfect progressive.
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The answer is A. not long after
Example: Bob forgot to lock the door. Not long after a thief noticed the unlocked door and stole all of Bob's valuables.
