Which one illustrates it?
A) III
B) II
C) I
D) IV

Circuit diagram number II
I) R=(4*8)/(4+8)=8/3 Ω
II) R=4+((4*4)/(4+4))= 6 Ω
III) R= 4/3 Ω
IV) the same as I: 8/3 Ω