Which of the following accurately describes semiconductor diodes? a. unlike junction diodes, point-contact diodes are enclosed in a suitable casing and have terminals for connecting them to a circuit. b. unlike point-contact diodes, junction diodes utilize a point of metal wire in contact with a single wafer of p-type or n-type material. c. junction diodes are preferred over point-contact diodes for most purposes. d. point-contact diodes are more likely to be used as rectifiers than junction diodes.