Positive Externalities Create Problems Within a Price System in the Sense

Positive externalities create problems within a price system in the sense that

A) if consuming a good creates positive externalities, no one will want to consume it.
B) if producing a good creates positive externalities, no one will want to produce it.
C) if consuming or producing a good creates positive externalities, too many resources will be devoted to it.
D) if consuming or producing a good creates positive externalities, too few resources will be devoted to it.