Definition: 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.
Input: Sentence1: My laboratory professor was explaining today's lab. Sentence2: He told us not to pour water followed by an acid. Sentence3: While I was looking at my notes, I barely paid attention. Sentence4: When the experiment began, I poured water before an acid in a tube.

My professor was very upset.