It's black,but you say it's clean .it's white ,but you say it's not clean. What is it?

问题描述:

It's black,but you say it's clean .it's white ,but you say it's not clean. What is it?

黑板

黑板
blackboard
chalkboard

它是黑色,但你说是干净的. 它的白色,但你说是不是干净. 是什么呢?

hair

black board