Identify the semiconductor devices whose characteristics are given above in the order (a), (b), (c), (d):

Simple diode conducts only in forward bias. It does not conduct in reverse bias. Zener diode conducts in forward bias. When reverse bias potential is increased, at a point zener breakdown occurs and then it behaves as a voltage regulator. Solar cell current is composed of dark current and forward-bias current. Resistance of LDR decreases with intensity of light.