You will be given a definition of a task first, then some input of the task.
You are given a sentence and a question in the input. The information provided in the sentence should be enough to answer the question. You're expected to write the correct answer. Do not use any facts other than those provided in the sentence.

Sentence: Emma's mother was in the back room she could safely cut up the tomato and place it on her sandwich without her mother knowing because she knew her mother would be upset.
Question: Why did Emma add the tomato to her sandwich when her mom was not in the room?
Output:
She knew her mother would be upset.