5.
Language study:
1. Many people keep dogs as pets because dogs are regarded as loyal friends to people.
regard....as
treat...as 把...看作...,视为
look on...as
think of...as
2. If you were on a deserted island, you would have to learn to collect water......
该句中用了虚拟语气，表示与现在事实相反的假设。从句中用过去式主句中would/should/might/could+动词原形。
If I knew the answer, I would tell you.
If I were you, I would buy it.
生词表: