Upper A sidewalkA$$sidewalk

is a$\_\_\_\_\_\_\_.$

A$.$

public goodpublic$$good

because it is rival and nonexcludablerival$$and$$nonexcludable

B$.$

natural monopoly goodnatural$$monopoly$$good

because it is both nonrival and nonexcludableboth$$nonrival$$and$$nonexcludable

C$.$

private goodprivate$$good

because it is both nonrival and nonexcludableboth$$nonrival$$and$$nonexcludable

D$.$

common resourcecommon$$resource

because it is rival and nonexcludable