The resistivity of water should not be less than 1000 Q m. This is because water is a good conductor of electricity, and if its resistivity is too low, it will allow electricity to flow through it too easily. This could cause problems in electrical appliances and equipment.
Option A is incorrect because 10 Q m is too low a resistivity. This would mean that water is a very good conductor of electricity, and it would allow electricity to flow through it too easily. This could cause problems in electrical appliances and equipment.
Option B is incorrect because 100 Q m is still too low a resistivity. This would mean that water is a good conductor of electricity, and it would allow electricity to flow through it too easily. This could cause problems in electrical appliances and equipment.
Option C is incorrect because 1000 Q m is the minimum resistivity that water should have. This means that water is a good conductor of electricity, but it will not allow electricity to flow through it too easily. This will not cause problems in electrical appliances and equipment.
Option D is incorrect because 2000 Q m is too high a resistivity. This would mean that water is a poor conductor of electricity, and it would not allow electricity to flow through it easily. This could cause problems in electrical appliances and equipment.