Four identical cells each have emf $E$ and internal resistance $r$. Match each arrangement with the single equivalent cell. List-I (Arrangement) A. All four in series B. All four in parallel C. In series, with one cell reversed D. Two parallel rows of two cells in series List-II (Equivalent cell) I. emf $2E$, resistance $r$ II. emf $E$, resistance $\dfrac{r}{4}$ III. emf $4E$, resistance $4r$ IV. emf $2E$, resistance $4r$