Three rods `A,B` and `C` have the same dimensions Their conductivities are `K_(A)` K and `K_(C)` respectively `A` and `B` are placed end to end with their free ends kept at certain temperature difference `C` is placed separately with its ends kept at same temperature difference The two arrangements conduct heat at the same rate `K_(c)` must be equal to .

Options

A. `k_(A)+k_(B)`
B. `(k_(A)k_(B))/(k_(A)+k_(B))`
C. `(1)/(2)(k_(A)+k_(B))`
D. `2.((k_(A)k_(B))/(k_(A)+k_(B)))`