Read the text and answer to the question

Travelling without parents.
If you want to go abroad, you have to take a form of ID with you. This could be a passport, or a national ID card, and it has to have your photo on it. You should also check out the rules for under 18s travelling on their own on the website of the embassy of the country you are going to. For example, for some countries, you need to have a letter from your parents giving permission for you to travel alone. If you don’t have that, you might find that you are not allowed into the country! You should also buy travel insurance in case anything happens, for example, if you lose your luggage or if you have a medical emergency.
The rules here depend on the different airlines. For most airlines, if you’re over 15 years old, you can travel alone. Remember that it’s easy to book a flight, but it’s also easy to miss it! You should make sure you get to the airport on time. For most flights you should get to the airport at least two hours before your flight. Although, if you are travelling to the United States, it’s three hours. The airline staff will make you show them your ID again – it’s normal, so don’t worry about that!
For accommodation, you should book a youth hostel because it’s cheaper and also you’ll be able to sleep in the same room as your friends. You shouldn’t choose somewhere that closes its doors at 8 pm. Many cheaper flights arrive after dinner and you don’t want to be left out on the street.
Why does the passage emphasize arriving at the airport early?
A) Because you need extra time to buy a ticket at the airport.
B) Because airlines cancel flights for late passengers.
C) Because airports do not allow check-in after a certain time.
D) Because you might miss your flight if you are late.