In "The Rockpile" by James Baldwin, the character that first identifies the rock pile as a dangerous place is A) Elizabeth.
In "The Rockpile", Elizabeth is the first one to believe that the rock pile is an unsafe place. She is the mother of Roy, John, Paul and Delilah and, at the same time, Gabriel's wife. Throughout the story, she sees her husband as a menace due to his violent behaviour. Elizabeth is also the one that defends John from Gabriel, his stepfather, after Roy gets hurt while playing on the rock pile.