Writing an black board with a piece of chalk is possible by the property of

Solution (By Examveda Team)

The correct answer is A: adhesive force.
Let's break down why:

Adhesive force is the attraction between different types of molecules.
Think of it like glue! The chalk sticks to the blackboard because of this attraction.

Cohesive force is the attraction between the same type of molecules.
This is what holds the chalk together as a solid, not what makes it stick to the board.

Surface tension is the property of a liquid that makes its surface behave like a stretched membrane.
It's not really relevant to chalk and blackboards.

Viscosity is a fluid's resistance to flow.
Think of honey versus water. Again, not relevant here.

So, the adhesive force is the key property that allows the chalk to stick to the blackboard and leave a mark.