When Did the Concept of Pornography as a Separate and Distinct

When did the concept of pornography as a separate and distinct category emerge in the United States?

A) In the middle of the 16th century (the mid-1500s)
B) In the late 17th century (the later 1600s)
C) In the middle of the 18th century (the mid-1700s)
D) In the early 20th century (the early 1900s)