Context: The airport was declared " closed " and we had to sit for 1.5 hours inside the plane . Apparently its related to trade union issues . Off we got , happy to arrive in the US of A and given we were the first plane to disembark rushed to passport control to avoid long lines of irritated passengers detained in other flights due to the storm . David joined the US citizen line and quickly went by , while Vero and Marcos slowly reached the customs officer in the " rest of states " line . Problem Number 1 : when we handed over our passport and customs slip to the officer he requested a green visa slip .

Question: Why did the officer request the visa slip ?
Options:
0. The trade union issues required visas to be displayed .
1. It is just standard protocol for every passenger of the plane .
2. Because he required payment for the flight we just took .
3. None of the above choices .
Answer: 3