Answer:
D.Jill is creating an external benefit for her neighbor.
Step-by-step explanation:
An external benefit is also called positive externality. This is a benefit that a transaction or activity provides to someone who is not part of the transaction or activity.
In this scenario Jill is the one who engaged in the activity of planting flowers. But her neighbor who is not a part of the activity is the one enjoying/benefitting from the flowers.