阅读下面短文，请完成短文后的2项测试任务：从第16-20题后所给的6个选项中为第①-⑤段每段选择1个正确的小标题。
The Pony (小马) Express
① In 1848, gold was found in California. Thousands of people rushed there. But the train line to California wasn't finished until 1869. It took a long time to ride a horse from California to Missouri. What would you do if you wanted to send a message? Well, you could use the Pony Express.
② In 1860 and 1861, the Pony Express was the fastest way to get news to and from the West. The road was around 2,000 miles long. It took most people weeks or months to ride that far. The Pony Express could make it in just 10 days. Those speeds were unheard of then. How did they do it? Well, they had a good system.
③ The Pony Express had 184 stations along the road. The stations were about 10 miles apart. This is about how far a horse could run before tired. The rider would switch to a new horse at each station. Every 75 - 100 miles, the rider would get to a home station, where riders would rest. Before resting, he would give his mail bag to a new rider. The mail never stopped moving, while the horses and riders rested.
④ It was tough to ride for the Pony Express. Each rider had to weigh less than 125 pounds. Speed was the key. Most riders were teenage boys. They rode up to 100 miles a day. The ride could be dangerous. Attacks by local people were common. But in its running time, the Pony Express lost only one mail bag.
⑤ The Pony Express filled an important role for a time, but it did not last. The Civil War started in 1861. Things got worse when the first telegraph line to California was finished later that year. People could send messages by telegraph instantly. Soon the Pony Express closed. But the story of the brave riders lives on.
Task 1
16. Paragraph ①:____
17. Paragraph ②:____
18. Paragraph ③:____
19. Paragraph ④:____
20. Paragraph ⑤:____
A. The end of riders’ business
B. The fastest message service
C. The comfortable home station
D. The effective system to send mail
E. Safe delivery despite the tough ride
F. Need of message exchange in the gold rush