[单选题]
In the following graph, the $V−I$ relationship for two different resistors $R_A$ and $R_B$ is displayed.
Which of the following statements is correct?
A. For both curves, the resistance can be found from the inverse of the gradient of the tangent at a point.
B. The resistance of A is never equal to the resistance of B
C. The gradient of the line for B gives the resistance of $R_B$
D. The resistance of A is always greater than or equal to the resistance of B.
