Two identical rods made of two different metals A and B with thermal conductivities $$K_A$$ and $$K_B$$ respectively are joined end to end. The free end of A is kept at a temperature $$T_1$$ while the free end of B is kept at a temperature $$T_2$$ $$( < T_1)$$. Therefore, in the steady state

A

the temperature of the junction will be determined only by $$K_A$$ and $$K_B$$.

B

if the lengths of the rods are doubled the rate of heat flow will be halved.

C

if the temperatures at the two free ends are interchanged the junction temperature will change.

D

the composite rod has an equivalent thermal conductivity of $$\frac{2K_A K_B}{K_A + K_B}$$.