题目内容：

阅读下面材料，在空白处填入适当的内容（1 个单词）或括号内单词的正确形式。

Tom and Jack are good friends. They have dreamed about __1.___( take) a great bike trip. It was Tom who first had the idea to cycle __2.____the entire Mekong River. They __3.___ (ride) bicycles to travel along the Mekong River, ___4.___source is in Qinghai Province. When it enters Southeast Asia, it travels slowly through low valleys to the plains, __5.___ rice grows. ___6.___ the difficulties , Tom and Jack were determined to begin their journey at an altitude of __7.___( much) than 5,000 metres in Qinghai Province. During their journey , they enjoyed the continuous change of the weather. ___8.__(finally), they reached Dali in Yunnan Province , where David and Sam joined__9.__.   __10.__ four of them  went on with their great bike trip.