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:
0. Because the boy lost his first tooth .
1. Because the boy is moving away .
2. None of the above choices .
3. Because the boy is growing up .
Answer: 3