Conductor having very high resistance
A conductor is a material that allows the flow of electric current. The ability of a material to conduct electricity is determined by its resistance. Resistance is the opposition offered by a material to the flow of electric current. It is measured in ohms (Ω).

When a conductor has a very high resistance, it means that it offers a significant opposition to the flow of electric current. This can be due to various factors such as the nature of the material, its dimensions, or the presence of impurities.

Options:
a) Insulator
b) Resistor
c) Semiconductor
d) Good conductor

Explanation:
The correct answer is option 'A' - Insulator. Here's why:

Insulator:
- An insulator is a material that has very high resistance to the flow of electric current.
- Insulators prevent or greatly restrict the flow of electric current through them.
- They have tightly bound electrons that do not move freely, making it difficult for electric current to pass through.
- Examples of insulators include rubber, plastic, glass, and wood.

Resistor:
- A resistor is a component specifically designed to have a specific resistance.
- It is used to control or limit the flow of electric current in a circuit.
- Resistors are made from materials that have moderate to high resistance.
- Examples of resistors include carbon composition resistors, metal film resistors, and wirewound resistors.

Semiconductor:
- A semiconductor is a material that has properties between those of a conductor and an insulator.
- Semiconductors have moderate resistance and can conduct electric current under certain conditions.
- They are widely used in electronic devices, such as transistors and diodes.
- Examples of semiconductors include silicon and germanium.

Good conductor:
- A good conductor is a material that has a low resistance to the flow of electric current.
- Good conductors allow electric current to flow easily through them.
- Examples of good conductors include metals such as copper, aluminum, and silver.

In conclusion, a conductor having very high resistance is an insulator. Insulators have high resistance and restrict the flow of electric current.