Del circuito de compuertas podes deducir directamente:
S = A'B' + BC
La tabla de verdad sería:
A ...............B..............C...................A'B' ...............BC ..................S
0.................0..............0.....................1....................0....................1
0..................0..............1....................1.....................0...................1
0..................1..............0....................0.....................0...................0
0..................1..............1....................0......................1...................1
1...................0..............0..................0.......................0...................0
1...................0..............1................. 0......................0....................0
1...................1...............0.................0......................0.....................0
1....................1...............1.................0......................0....................0