Read the following context and choose the best option to answer the question.
Context: Our first day of school was filled with excitement and a little sentiment . The husband and I dropped the little boy off to school and as you can see he 's very ready . He woke up early , ate breakfast and got dressed all by himself .
Question: What may be the reason for this day being sentimental ?
Options: 
- Because the boy lost his first tooth .
 - Because the boy is moving away .
 - None of the above choices .
 - Because the boy is growing up .


Because the boy is growing up .