Answer:
a. a rightward shift of the demand curve.
Step-by-step explanation:
An increase in demand is reflected graphically as a rightward shift of the demand curve.
A decrease in demand is reflected graphically as a leftward shift of the demand curve.
An increase in Quanitity demanded is represented as a movement down the demand curve.
A decrease in quantity demanded is represented as a movement up the demand curve.
Please check the attached image for a graph showing the rightward shift of the demand curve.
I hope my answer helps you