What is black when it is clean and white when it is dirty?

it is clean when it is black.it is dirty when itis white.what is it 智力测试What is black when it is clean and white when it is dirty? What is clean when it is black and dirty when it is white? What is black when it is clean white when it is dirty? what is black when it is clean and white when it is dirty是----- What is black when it is clean and white when it is dirty? What、is、black、when、it、is、clean、and、when、it、is、dirty·谜底是什么? It is clean when it is black.It is clean when it is black.It is dirty when it is white.what's it? 【what is clean when it black ,and white when it is dirty. 猜谜语：It is clean when it is black.It is dirty when it is white.What's it 英语：读一读,想一想,猜一猜What is black when it is clean and white when it is dirty?It is a ( ). When I am clam ,I am black .When I am dirty,I am white.What am 智力题 What is black when it is clean and white when it is dirty?求求啦!我弟的寒假作业. what is black when it is clean and white when it is dirty?用英语怎么回答 What is'the Penny Black'? 英语翻译What is Mr Black? 英语趣味问和答 What is black when it is clean and white when it is dirty?What is the poorest in the world?Why are dogs afraid to sunbathe?what two words contain thousands of letters?why is 10*10=1000 like your left eye?Why is the letter E so i I am black when you get me,red when you use me,and white when you're all through with me.What am I动动脑筋啦