OpenStax College Physics for AP® Courses, Chapter 20, Problem 8 (Test Prep for AP® Courses)

This is College Physics Answers with Shaun Dychko. With this question, you have to really pay attention to the way it's worded: it's asking which of the following affect the resistivity of a wire; it's not asking which of the following affect the resistance of a wire. The resistance of a wire is the resistivity, which is this factor ρ multiplied by the length of the wire divided by its cross-sectional area but it's the ρ that this question is asking about so what affects ρ? Well, resistivity is some original resistivity at some you know standard temperature times 1 plus the temperature coefficient of resistivity for the material times change in temperature but temperature doesn't appear anywhere in our list of options and so the only thing that will matter is this material because different materials have different resistivities at certain standard temperatures. So the answer to this question is (c).