根据句子意思，用括号中所给单词的适当形式填空。（每小题1分，共5分）
The story happened about two         (century) ago.
Besides the funny actors in the film, the story          (it) is really interesting.
In China, the number “eight” is thought to be a           (luck) number by many people.
We can make a big difference to the earth by          (do) small changes.
The elephant is seriously ill. It is        (die).