Answer $\rightarrow$ D$(a=00,b=10,c=01,d=11)$
$S_A = \overline A$
$R_A = A$
( here we see that $S_A$ and $R_A$ are always complemented)
Next $(A)=\overline A$
$S_B = A.\overline B$
$R_B = A.B$
If $\overline A, S_A=0,S_B=0$,$B$ stays same.
If $A$ then Next $(B)=\overline B$
Next $(B)=A.\overline B + \overline A.B$
$X=A.B$
Now,
- Current $(A,B)=(0,0)$ ; $X=0.0=0$ ; Next $(A,B)=(\overline A,\space B)=(1,0)$
- Current $(A,B)=(1,0)$ ; $X=1.0=0$ ; Next $(A,B)=(\overline A,\space \overline B)=(0,1)$
- Current $(A,B)=(0,1)$ ; $X=0.1=0$ ; Next $(A,B)=(\overline A,\space B)=(1,1)$
- Current $(A,B)=(1,1)$ ; $X=1.1=1$ ; Next $(A,B)=(\overline A,\space \overline B)=(0,0)$