a) i) What is meant by a semiconductor? ii) Distinguish between intrinsic and extrinsic semiconductors. b) i) With the aid of a labelled diagram, describe the structure of a p-n junction diode. ii) Explain what is meant by forward biasing and reverse biasing of a p-n junction diode. iii) Sketch the current-voltage (I-V) characteristic curve of a p-n junction diode, labelling the axes and indicating the forward and reverse bias regions. c) State TWO practical applications of a p-n junction diode.