(Saw : Wood) , (Pen : Paper) , (Author : Book) , (Chalk : Blackboard)
Option:
Justification: In all other pairs, first is the tool which works over the second.

(Saw : Wood) , (Pen : Paper) , (Author : Book) , (Chalk : Blackboard)
Justification: In all other pairs, first is the tool which works over the second.