I'm taking a test and have to guess the right answer to the question after the article. Article: More often than not, the person sitting next to you on a plane or sleeping in the next hotel room has paid more or less than you did for the same services. Each day, airlines give more than several hundred fares for flights between the same two cities and hotels charge different rates for the same room. So how do you find the best rates? Here are some tips: ^ Sign up for fare special e-mails. When airlines get into a fare war, the cost of a plane ticket can fall overnight and the discounted fare may be sold out by noon the next day. Get on the mailing list of airlines and other travel Web sites so you can be told immediately if fares drop. ^ Buy your tickets at least 21 days in advance. There are usually four different timetables for advance tickets: 21-day, 14-day, 7-day, and 3-day. The further in advance you book your flight, the lower the fare you will find. ^ Consider another airport. Find out about all the airports that are near your destination city. You might be able to fly into a smaller airport or neighboring city at a much lower rate. ^ Stay over a Saturday night. Airlines give the highest fares to business travelers, who fly during the week and spend their weekends at home. If you plan to leave for your trip on a Wednesday and return on Saturday, your fare would be a lot higher than you stay until Sunday morning. ^ Fly on Tuesdays, Wednesdays, and Saturdays. Some airlines offer cheaper fares on different days of the week. Generally, it's the cheapest to fly on Tuesday, Wednesday, and Saturday. Remember, though, that a Saturday stay is necessary to receive the lowest rate. ^ Pick a flight with plenty of open seats. Seats in a flight are divided into "classes", and each class has its own price. Since the cheapest classes sell first, the fewer seats that are left on a plane, the more expensive they are. Question: This passage is mainly about _ . Options: A: how to keep yourself safe during your flight B: how to choose a better and more comfortable airline C: how to spend less when traveling by air D: how to book your air ticket in advance
A:
C