If serial input $=1111,$ shift register $A=0101,$ shift register $B=0100$

What will be the content of Shift register A and $B$ after $4$ triggering

shift register $A=111,$ shift register $B=1001$

shift register $A=0000$ shift register $B=1001$

shift register $A=0000,$ shift register $B=0000$

shift register $A=1001,$ shift register $B=1111$