A. Single-pole relay
B. DPDT switch
C. Rotary switch
D. Linear stepper
This question was posed to me in a national level competition.
I want to ask this question from Multiplexers (Data Selectors) in section Combinational Circuits of Digital Circuits
The explanation: A basic multiplexer principle can be demonstrated through the use of a rotary switch. Since its behaviour is similar to the multiplexer. There are around 10 digits out of which one is selected one at a time and fed to the output.