The voltage-current variation of two metallic wires $X$ and $Y$ at constant temperature are shown below. Assuming that the wires have the same length and the same diameter, explain which of the two wires will have larger resistivity.

(B) The graph shows the variation of current $(I)$ on the $y$-axis with respect to voltage $(V)$ on the $x$-axis.
According to Ohm's law, $V = IR$, which implies $I = (1/R)V$.
The slope of the $I-V$ graph is given by $\text{slope} = I/V = 1/R$.
From the graph, the slope of line $X$ is greater than the slope of line $Y$ $(\text{slope}_X > \text{slope}_Y)$.
Since $\text{slope} = 1/R$, this means $1/R_X > 1/R_Y$, which implies $R_X < R_Y$.
Resistance $(R)$ is related to resistivity $(\rho)$ by the formula $R = \rho(L/A)$.
Given that both wires have the same length $(L)$ and the same diameter (and thus the same cross-sectional area $A$), the resistance is directly proportional to the resistivity $(R \propto \rho)$.
Since $R_Y > R_X$, it follows that the resistivity of wire $Y$ is greater than the resistivity of wire $X$ $(\rho_Y > \rho_X)$.