Which of the following best describes a good conductor?

A good conductor is characterized by low resistance and the ability to allow electric current to flow easily. Materials that exhibit these properties, such as copper and aluminum, have a high number of free electrons that can move freely, enabling efficient transmission of electrical energy.

In contrast, high resistance materials tend to impede the flow of current, which is the opposite of what is desired in a good conductor. Additionally, materials with a high temperature coefficient might not be reliable conductors under varying temperature conditions. Lastly, inflexible and brittle materials do not typically make effective conductors because their physical properties can lead to breaks or defects that disrupt the flow of electricity.

Therefore, the defining characteristic of a good conductor is indeed its low resistance and ability to facilitate easy flow of electric current.