In this task, you're given a four sentences of story written in natural language. Your job is to complete end part of the story by predicting appropriate last sentence which is coherent with the given sentences.

Sentence1: Joyce was at the mall. Sentence2: And she saw one of her classmates, Jill. Sentence3: Joyce waved to her but received no response. Sentence4: At school the next day, Joyce asked Jill why she didn't wave back.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
But Jill just didn't see Joyce.