阅读下列短文，从每题所给的四个选项(A、B、C、和D)中，选出最佳选项，并在答题卡上将该项涂黑。
A
If you're after cheap UK train tickets, check the suggestions below and see how you could bag yourself a bargain. We'll even highlight the cheapest prices!
·Booking in advance
Train tickets in the UK usually go on sale 3 months before the date of travel. Look out for advance tickets, as these tend to be cheaper when they're first released. Be quick though, as they may sell out on busier routes.
Find out more about our advance ticket alarm tool.
·Traveling off-peak
When travelling by train in the UK, you can benefit from reduced fares by choosing the time periods of day that are less busy. When searching for tickets with us, we'll display all available ticket options, highlighting the cheapest ones.
Learn more about off-peak train time from our website.
·Using the price prediction tool
Our clever little price prediction tool will predict the future and let you know when ticket prices are about to go up, meaning you'll never miss out on the best value fares. Beat the rush and save on price too (Currently available in the UK app only).
Discover the magic of price prediction.
·Choosing the season ticket calculator
If you travel on the same route more than three times a week, then season tickets could help you to save both valuable time and money. Besides that, they're also available in a number of flexible options to suit different time frames.
Check out our season ticket calculator today to get started.
21. What is the characteristic of traveling off-peak by train in the UK?
A. The trains are too crowded. B. Train tickets are often sold out.
C. There are more passengers at this time. D. The travel time periods are less busy.
22. What can visitors do if they want to know when train fares will rise?
A. Call ahead and ask. B. Check the advance ticket alert tool.
C. Refer to a piece of price prediction tool. D. Download the season ticket calculator.
23. What is the author's main purpose in writing the text?
A. To advertise train services.
B. To encourage passengers to travel abroad.
C. To offer services to the train passengers on the way.
D. To help visitors spend less money on railway tickets.
