Resistivity does not change ifA. The material is changedB. The temperature is changedC. The shape of the resistor is changedD. Both material and temperature are changed.

The correct answer is C. The shape of the resistor is changed.

Resistivity is an intrinsic property of a material and is independent of the shape of the object made from that material. Resistivity is a measure of how strongly a material opposes the flow of electric current. It is determined by the type of material and its atomic structure, not by the shape of the object.

Option A is incorrect because resistivity does change if the material is changed. Different materials have different resistivities, which affect their ability to conduct electric current.

Option B is incorrect because resistivity does change if the temperature is changed. In general, most materials experience an increase in resistivity as temperature increases. This is due to increased collisions between electrons and lattice vibrations, which hinder the flow of current.

Option D is also incorrect because it combines options A and B, both of which are individually true. Changing the material or the temperature can both alter the resistivity of a material.