Which of the following is used in exocytosis

Exocytosis, in most cases, is stimulated by the entry of calcium ions into the cell; calcium ions interact with the vesicular membrane in some way that is not understood and cause its fusion with the cell membrane, followed by exocytosis--that is, opening of the membrane's outer surface and extrusion of its contents outside the cell.Ref: Guyton; 13th edition; Chapter 2; The Cell and Its Functions