Answer: D. a common resource when it is congested, but it is a public good when it is not congested.
Explanation: A public good is a good that individuals cannot be excluded from its use and the use of it by one individual does not reduce its availability to others while a common resource is a resource which no individual can be excluded from using, but it's availability may be subject to rivalry.
Therefore during congestions, a city street is a common resource as availability for use is limited and a public good when it is not congested as there's both access and availability for use.