五道初三英语词转题.根据所给内容,用其正确形式填空.（求详细解析!）The Grand Canyon is one of

根据所给内容,用其正确形式填空.（求详细解析!）

The Grand Canyon is one of the greatest ________（nature) wonders of the world.

It's amazing that the baby is still _______(live) in the accident!

During this year,we learned a lot of _______(knowledge) from the teachers.

In fact,there are many _______(difference) between the twin brothers although they look the same.

You should give up ________(smoke) because it has done great harm to your health.

附1-3题答案：1.natural（为何这样变形?） 2.alive 3.knowledge（为何不变复数?）

4、5两题我对老师给我的答案存疑,附：4.differentes 5.smorking

不只求答案,更求大神的解析!