Context: The police officers ascended the steps and checked every passport individually . I was again surprised when I did n't get my passport stamped . Once you cross one border within Central America , a stamp is not necessary until you leave the region .

Question: Why did the police check each passport ?
Options:
0. To find a lost child based on their ID
1. To help out the border control agents
2. To try to return a laptop that they found
3. To check for criminals entering the country
Answer: 3