Multiplexer: A digital multiplexer can be used for parallel to serial conversion and as many to one switch. Multiplexer is also known as data selector that selects between several analogy or digital input signals and forwards it to a single output line. Multiplexer with n select line contains 2n inputs and a single output. A multiplexer is also known as parallel to serial converter or many to one circuit. A multiplexer can be used to implement if-else statements. So, here selection line is used to select the inputs for the output. For 2n inputs, there are n select lines that determine, which input is to be connected to the output [ alt="F1 R.S Shraddha 17.02.20 D1" src="//storage.googleapis.com/tb-img/production/20/02/F1_R.S_Shraddha_17.02.20_D1.png" style="width: 147px; height: 127px;"> Y = S̅ B + SA Note: Decoder is used for chip select not MUX. Hence option 3 is correct.