Why Did Slavery Come to Be Known as "The Peculiar

Why did slavery come to be known as "the peculiar institution" in the first half of the nineteenth century?

A) It spawned new African American religious and cultural practices that white Americans found deeply alien.
B) As slavery faded away in the North, it was increasingly associated with the South, where it became more entrenched.
C) The three-fifths compromise in the Constitution seemed increasingly strange and outdated to Southerners.
D) As the free black population grew larger than the slave population in America, slaves became the exception rather the norm among African Americans.
E) The end of American participation in the international slave trade in 1807 made slavery seem a doomed throwback to colonial times.