Which Is an Example of an External Benefit

Which is an example of an external benefit?

A) You get a raise that increases your pay 20%.
B) Your neighbor's rooster wakes you up every morning before your alarm clock goes off, reducing the amount of sleep you get at night.
C) Researchers at Johnson & Johnson are working on a cure for cancer.
D) Your neighbors fix up their homes, which raises property values on the entire street.