A.10111+11101=10100(溢出); B.10111+11101=10100(未溢出); C.11001+10010=01011(溢出); D.11001+10010=01011(未溢出);
A.10111+10100=11011; B.11011+11100=10111; C.11001+11100=10101; D.01011+11011=00110;
A.01011+10100=11111; B.01011+10100=00111; C.01011+11100=00111; D.01011+11011=00110;