Consider the following sub$\_$module$\_$verilog code:

module sub$-$module$-$verilog $($input A$,$ B$,$ output wire $M,N,S)$;

Assign $M=A{}^{{?}^{?}}B$;

Assign $N=A$ & $B$;

Assign $S=A$&$B$;

endmodule

Consider the following main$\_$module$\_$verilog code:

The module described above represents