5. It’s probable that traders along the Silk Road needed________.
A. to remember the entire trade route
B. to know the making of products
C. to receive certain special training
D. to deal with a lot of difficulties
[解析] 细节理解题。根据“The routes crossed mountains and deserts and had many dangers of hot sun，deep snow and even battles.Only experienced traders could return safe.”可知D项正确。
[答案] D
