During exercise, venous return of blood to the heart increases. based on your knowledge of starling's law, what would happen to stroke volume during exercise?

The stroke volume of the heart will also rise since exercise is the process where heart is working with great internal pressure or we can say it is in a state of being distended, this ultimately will cause a greater strength of contraction.

This is just in accordance with Stroke’s law that states that stroke volume of the heart increases if the volume of blood in the ventricles, before contraction if all other factors remain same or unchanged. When a large amount of blood rushes in the ventricle, it stretches the muscle fibers of heart that ultimately causes a rise in the force of contraction.  

Significance:

This actually helps in the synchronization of output from heart with arterial blood supply, venous return and humoral length without regulating or producing any other changes in the body.