Riddle

I am clean when I'm black, dirty when I'm white. What am I?

Choose an answer

A.Whiteboard
B.Notepad
C.Blackboard eraser
D.Chalkboard
Hint: It's a word with 10 letters, starting with "C".

Answer

Chalkboard

Why this is the answer

A chalkboard looks "clean" when its black surface is bare, and "dirty" once covered in white chalk dust -- the reverse logic of the blackboard riddle earlier in this set.

This riddle is filed under "What Am I?" Riddles and rated Easy.