完成句子。

1. He has to learn ________ (收集淡水),hunt for food,and make fire.(how)

2. 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)

3. How did these differences come about? There is _________ (没有直截了当的答案) this question.(answer)

4. Businessmen and tourists often come to China ___________ (但不会说) Chinese.(without)