Option A) Very low is incorrect because the temperature coefficient of resistance for most conductors is positive, which means that their resistance increases with increasing temperature. Therefore, Ohm's law is still valid for a conductor at a very low temperature, as long as the temperature remains constant.
Option B) Very high is also incorrect because the temperature coefficient of resistance for most conductors is positive, which means that their resistance increases with increasing temperature. Therefore, Ohm's law is still valid for a conductor at a very high temperature, as long as the temperature remains constant.
Option C) Varying is also incorrect because Ohm's law is only valid when the temperature of the conductor remains constant. If the temperature varies, then the resistance of the conductor may also vary, and Ohm's law may no longer be applicable.
Option D) We know that for a material to obey Ohm's law, the resistance must remain constant. We know that resistance = pL/A, where p is the resistivity. The resistivity of a conductor is dependent on its temperature and therefore if temperature changes, resistivity too changes. Consequently, the resistance will also change and Ohm's Law will no longer hold.

Very low is incorrect because the temperature coefficient of resistance for most conductors is positive, which means that their resistance increases with increasing temperature. Therefore, Ohm's law is still valid for a conductor at a very low temperature, as long as the temperature remains constant.

Very high is also incorrect because the temperature coefficient of resistance for most conductors is positive, which means that their resistance increases with increasing temperature. Therefore, Ohm's law is still valid for a conductor at a very high temperature, as long as the temperature remains constant.

Varying is also incorrect because Ohm's law is only valid when the temperature of the conductor remains constant. If the temperature varies, then the resistance of the conductor may also vary, and Ohm's law may no longer be applicable.

We know that in order for a material to obey Ohm's law, the resistance must remain constant.

We know that resistance = pL/A,

where p is the resistivity. The resistivity of a conductor is dependent on its temperature and therefore if temperature changes, resistivity too changes.

Consequently, the resistance will also change and Ohm's Law will no longer hold.