Which is a pair of geometrical isomers?
I. \begin{matrix} Cl & & & & & & Br \\ & \diagdown & & & & \diagup & \\ & & C & = & C & & \\ & \diagup & & & & \diagdown & \\ H & & & & & & Br \end{matrix}
II. \begin{matrix} Cl & & & & & & Br \\ & \diagdown & & & & \diagup & \\ & & C & = & C & & \\ & \diagup & & & & \diagdown & \\ H & & & & & & CH_3 \end{matrix}
III. \begin{matrix} Cl & & & & & & CH_3 \\ & \diagdown & & & & \diagup & \\ & & C & = & C & & \\ & \diagup & & & & \diagdown & \\ Br & & & & & & H \end{matrix}
IV. \begin{matrix} H & & & & & & Br \\ & \diagdown & & & & \diagup & \\ & & C & = & C & & \\ & \diagup & & & & \diagdown & \\ CL & & & & & & CH_3 \end{matrix}
(a) I and III
(b) II and IV
(c) III and IV
(d) I and II
(b) II and IV