In the measurement of resistance of a wire using Ohm's law, the...

We know $V ∝ I$, so $V - I$ curve for a ohmic devices is a straight line passing through origin. Due to some errors/carelessness during experiments, all points may not come on the same line. In this situation, we draw the most appropriate curve.

From given $V - I$ curve,
$⇒ R = \dfrac{2.5}{2.5} = 1Ω$