Two resistors, labeled A and B , have resistances R_A and R_B...

The resistance of a conductor is given by $R = \rho \dfrac{l}{A}$

where $\rho$ is the resistivity of the material, $l$ is the length, and $A$ is the cross-sectional area.

Given $R_A < R_B$, we have $\rho_A \dfrac{l_A}{A_A} < \rho_B \dfrac{l_B}{A_B}$

Since the dimensions ($l$ and $A$) of the two resistors are not provided, we cannot compare the resistivities $\rho_A$ and $\rho_B$.

The provided information is insufficient to establish a relation between $\rho_A$ and $\rho_B$.