Hint: In order to reach the correct answer from the above options we need to define each of the substances mentioned above. Further we need to know whether the number of free electrons are available or not and satisfies the requirements of the question. Accordingly then we manipulate the above incorrect option from the ones provided.
Complete step by step answer:
Let us first understand a bit about the above mentioned substances.
Insulators: These are the substances that do not conduct electricity. The energy gap between the conduction band and the valence band is so vast that they do not conduct flow of charges easily.
Inductor: It is basically a coil, when connected to an emf generates back emf by electromagnetic induction. It allows the flow of current through it only in a steady state of current.
Semiconductors: These are substances that conduct electricity at suitable temperatures . This is because the electrons gain sufficient thermal energy to overcome the gap between the conduction and valence band. Normally there are no electrons in the conduction band of semiconductors.
Conductors: These substances conduct electricity at any given temperatures. Normally there are sufficient electrons in the conduction band as their conduction and the valence band overlap with each other i.e. metals.
Hence the correct answer from the above definition is conductors.
So, the correct answer is “Option d”.
Note: It is to be noted that the conduction of the semiconductors increases with increase in temperature. Whereas for metals the conduction increases with the decrease in temperature. At a particular lower temperature the metals can offer zero resistance, such substances are called superconductors.