Question

work is a scalar quantity.give reason

Answer 1

Work doesn't depend on the direction. We can always change the direction of the applied force using pulleys etc. 

Answer 2

Scalar quantities are those which have only magnitude and no direction.
Work is said to be done when a force that is applied on a body moves that body i.e causes a displacement.
So work is the product of force and displacement: W=F*d

Now Force and Displacement are both vectors and the dot product of two vectors is always a scalar quantity.

Also, work is a part of the energy of the system and energy is a scalar quantity.