a) Sketch the Van Deemter composite Curve and elaborate the benefit of using nitrogen gas as compared to using hydrogen gas as mobile phase in Gas Chromatography. (4 marks) b) Explain the term "temperature programming" method and give one (1) advantage of this method over isothermal run method. (3 marks) c) Relate the benefit of Chemical derivatization in Gas Chromatography. (4 marks) d) With the aid of diagram, briefly discuss the principle of Gas Chromatography (GC). (4 marks)