Then rows each containing n cells in series are joined in parallel. Maximum current is taken from this combination across an external resistance of 3Ω. If the total number of cells used is 24 and internal resistance of each cell is 0.5Ω, then

The correct option is C m=12,n=2
Current is maximum when equivalent resistance is equal to external resistance of 3 ohm.
Now total resistance is m × 0.5/n. (Resistances are parallel so they are directly added to each other)
According to question:
m × 0.5/n = 3
→ mn = 6
As the ratio of m and n is 6, then the best option which satisfies this relation is option C