以下的描述中，必然是对Mealy型状态机的描述的是？

A、always @(*) case (state) S0: begin out = 0; if (in) next_state = S1; else next_state = S2; end ……
B、always @(*) case (state) S0: begin if (in) next_state = S1; else next_state = S0; end ……
C、always @(*) case (state) S0: begin if (in) begin next_state = S1; out=1 end else next_state = S0; end ……
D、以上答案均不正确