完成句子。

He has to learn ____ （收集淡水),hunt for food,and make fire.（how)The lesson we can learn from Chuck and all the others ____ （结交了不同寻常朋友) is that friends

  are teachers.（unusual)

How did these differences come about？ There is _____ （没有直截了当的答案) this question.（answer)Businessmen and tourists often come to China _____ （但不会说) Chinese.（without)