阅读下列材料，从每题所给的四个选项(A、B、C和D)中，选出最佳选项。
A
Three Days Dunhuang Bike Tour
Going on a bike is a great way to explore the natural beauty of Dunhuang. Our tour is spent riding along the country road and the edge of town where we'll pass by country houses, farmlands and vineyards (葡萄园) to show you the beauty of the little oasis (绿洲) in the desert.
Day 1
Meals：None
Accommodation (住宿)：In Dunhuang
You will be picked up at the train station and moved to the hotel once you arrive in Dunhuang. Free for the rest of the day. Dunhuang is located on the western end of Hexi Corridor, at the meeting point of Gansu, Qinghai and Xinjiang in the Northwest of China.Known as Shazhou in ancient times, Dunhuang served as a rest stop for traders and due to its special geographical location, it was the gateway through which many religions (宗教) like Buddhism, Islam and Christianity entered China.
Day 2
Meals：Breakfast, Lunch
Accommodation：In Dunhuang
You need to get up and start biking early in the morning. First, we will ride 30 minutes to the Mogao Caves (10 km) and visit the biggest Buddhist art gallery of the world. After lunch, we will ride bike to the White Horse Pagoda which is located in the countryside (12 km) and was built in 386 A．D.in memory of the white horse of the greatest Buddhist translator, Kumarajiva. Then we will have dinner at a local farmer's restaurant. In the evening, we will ride a bike to the famous SingingSand Dunes and Yueyaquan (6 km). Finally, we will ride back to the hotel.
Day 3
Meals：Breakfast
Accommodation：None
Be dropped off at the airport and call it a day.
21．What can the riders do during the tour?
A．Enjoy the beauty of the countryside.
B．Find the best way to visit Dunhuang.
C．Have to put up with the heat in the desert.
D．Go cycling in downtown Dunhuang.
22．Dunhuang once had various ________.
A．horse races
B．tourism programs
C．business activities
D．Buddhist arguments
23．What can we know about the Mogao Caves and the White Horse Pagoda?
A．They hold art exhibitions.
B．They have places for horses.
C．They have religious backgrounds.
D．They are tourist information centers.
