Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: Luke 's fish died . Just before I was going to put the boys down for the evening , Wendy came upstairs and mentioned to me in a somber whisper , " Luke 's fish died . Should we tell him now , or should we wait till the morning ? " I could n't stand the idea of my son sleeping peacefully while his fish was belly up in the tank , so I said she better go tell him right away .

Question: Why might Luke not sleep well that night ?
He is upset by a loss
Luke might not sleep well because his fish died.