根据句意，用括号中所给词的适当形式填空，并将答案写在答题卡的相应位置上。

【1】It’s ____________ to talk with your mouth full.（polite）

【2】Edison was a great ____________. (invent)

【3】The old man made a living by ________________old thing. (sell)

【4】I have been to Lijiang ______________. I think it’s really beautiful. (two)

【5】They are old enough to look after ______________. (they)