Runners in a relay race pass a stick in one direction. However, merchants passed silk, gold, fruit, and glass along the Silk Road in more than one direction. They earned their living by traveling the famous Silk Road. The Silk Road was not a simple trading network. It passed through thousands of cities and towns. It started from eastern China, across Central Asia and the Middle East, and ended in the Mediterranean Sea. It was used from about 200 BC to about 1300 AD, when sea travel offered new routes. It was sometimes called the world's longest highway. However, the Silk Road was made up of many routes, not one smooth path. They passed through what are now 18 countries. The routes crossed mountains and deserts and had many dangers of hot sun, deep snow and even battles. Only experienced traders could return safe. The Silk Road got its name from its most prized product. Silk could be used like money to pay taxes or buy goods. But the traders carried more than just silk. Gold, silver, and glass from Europe were much found in the Middle East and Asia. Horses traded from other areas changed farming practices in China. Indian merchants traded salt and other valuable goods. Chinese merchants traded paper, which produced an immediate effect on the West. Apples traveled from central Asia to Rome. The Chinese had learned to graft   different trees together to make new kinds of fruit. They passed this science on to others, including the Romans. The Romans used grafting to grow the apple. Trading along the Silk Road led to world-wide business 2,000 years before the World Wide Web. The people along the Silk Road did not share just goods. They also shared their beliefs. The Silk Road provided pathways for learning, diplomacy, and religion. It's probable that traders along the Silk Road needed   _  .
to deal with a lot of difficulties to know the making of products to receive certain special training to remember the entire trade route