A. One of the characteristics of the gothic writing is that the setting serves as a way of evoking a sense of mystery. More often than not the places in a gothic story have pasts and secrets that may or may not interfere in the narrative. In the excerpt, Ichabod rides through a tree that is associaded with the tragedy of Major André.
B. "Suddenly, he heard a groan-his teeth chattered and his knees smote against the saddle(...)"
C. The foreshadowing in the excerpt probably indicates something frightful that will happen to Ichabod.