Lightning is due to

Lightning is a massive electrostatic discharge caused by the imbalance of electrical charges. While lightning occurs within clouds (intra-cloud), the specific mechanism leading to a strike on Earth involves electrostatic induction.

• Charge Separation: During a storm, collisions between ice crystals and water droplets cause the base of the cloud to become heavily negatively charged, while the top becomes positively charged.
• Induction on Ground: This concentrated negative charge at the cloud's base repels electrons on the Earth's surface, creating a strong induced positive charge on the ground, trees, and buildings below.
• Electrical Breakdown: When the potential difference between the cloud base and the ground becomes high enough to overcome the air's resistance, a discharge occurs, resulting in a lightning strike.

Therefore, Option D is correct as it describes the fundamental process of induction that precedes a cloud-to-ground lightning flash.