What happens to some conductive materials' resistance as temperature increases?

As the temperature of conductive materials increases, the resistance generally varies due to the increased thermal energy affecting the charge carriers. For most conductive materials, such as metals, resistance tends to increase with temperature. This is because, as the temperature rises, the metal ions in the lattice structure vibrate more vigorously, which interferes with the flow of electrons, leading to a higher resistance. However, in some materials and scenarios, such as semiconductors, the behavior can be more complex, and resistance can decrease as temperature rises due to increased charge carrier concentration.

The term "varies" captures this complexity. It correctly indicates that the resistance does not follow a simple or consistent pattern for all materials. Hence, in the context of the different behaviors exhibited by various conductive materials when subjected to temperature changes, this option is the most accurate representation of the phenomenon.