Q. One that is not the outcome of magnitude comparator is                          

Explanation by: Mr. Dubey

 a comparator is a combinational circuit that takes two numbers as input in binary form and results whether one input is greater, lesser or equal to the other input. in a digital comparator, only 3 outputs are possible (i.e. a = b, a > b, a < b). so, a – b is incorrect option.