Read the excerpt from "remembering to never forget: dominican republic’s ‘parsley massacre’” by mark memmott.

passage a:

this week, people from around the world are expected to gather in the dominican republic for a "border of lights” commemoration that aims to "honor a tragedy long forgotten, and unknown to many people.”

passage b:

trujillo, as the border of lights website explains, fed and nurtured anti-haitian sentiment and created an atmosphere that still excludes ethnic haitians from becoming part of "the dominican melting pot.”

the method his soldiers used in 1937 to try to identify those who would be killed was cruelly unique. when confronting someone in the lands along the border with haiti, they would hold up a sprig of parsley and ask what it was. if the person responded by trilling the "r” in perejil (spanish for parsley), he would be free to go. anyone who didn't trill the "r” was thought to be a haitian creole speaker—and was likely to be killed.

how do these excerpts work together to develop a central idea?