Answer:
c. Internal benefits are less than external benefits
Explanation:
Lets first understand what a positive externality is. Positive externality is the effects of an activity that has greater and/or additional benefits to the society as a whole as compared to the benefits enjoyed by the individual responsible for creating such a positive impact. One of the common examples of positive externality is getting education, when we get education that provides us benefits on a personal level but it also helps you reach to a position where you can educate others and/or the society in general. This means that educating yourself not only benefits you but also has a positive influence in the society.
Similarly, if you walk to work every day, this will make you more healthy and will reduce congestion in the city and benefit every body else as well.