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