Concept:Gases conduct electricity when they become ionised under suitable conditions.
Explanation:At low pressure, gas molecules are few and far apart, making ionisation easier.
A high potential difference provides the energy needed to accelerate ions and electrons.
These fast-moving particles collide with neutral molecules, releasing more charge carriers.
This allows an electric current to pass through the gas.
Therefore, the required condition is low pressure and high p.d.
Answer:B. low pressure and high p.d.