S2 is also not true: You have〖E F b〗 = {s0,s1,s2} and thus〖a & E F b〗 = {s1}, thus 〖AX(a & E F b)〗 = {s0;s2}, and since these states cannot be visited only, it follows that S2 holds in none of the states. S1 does also not hold in s0 since the only path leaving there satisfies next that a holds, but then a becomes false so that Ga does not hold.