(C) R₃ > R₂ > R₁
In an I-V graph, slope = I/V = 1/R. A steeper slope means lower resistance. Since R₁ has the steepest slope, it has the least resistance, giving R₃ > R₂ > R₁.
The key concept: in an I-V graph, slope = 1/R (from Ohm's law, I = V/R). A steeper line → higher current for same voltage → lower resistance. R₁ is steepest, so R₁ is smallest; R₃ is least steep, so R₃ is largest. Students often confuse steeper slope with higher resistance — remember it is the inverse.