Optoisolator is
(a) A combination of LED and varactor in the same package
(b) A combination of a varactor and photodiode in the same package
(c) A combination of LED and a photodiode in the same package
(d) A combination of photodiode and Schottky-Barrier Diode in the same package
The question was asked in an interview for internship.
My question is taken from Limiting and Clamping Circuits and Some Special Types of diodes topic in section Diodes of Electronic Devices & Circuits