用括号内所给单词的正确形式填空。
1. It is said that potato chips in KFC _____ (invent) by mistake about one hundred years ago.
2. It is reported that the Underground Line No.3 _____ (build) next year.
3. Metal _____ (use) for making machines and many other things.
4. Nick _____ (offer) a job in a bank, but to our surprise, he didn't take it.
5. Trees and flowers _____ (plant) every year to make our country more beautiful.