Lighting occurs due to

Options

A. rain
B. wind
C. humidity
D. electric discharge

Explanation

### Step-by-Step Solution:

1. **Understanding Lightning**:
- Lightning is a natural phenomenon that occurs during thunderstorms. It is characterized by bright flashes of light, which we see in the sky.

2. **Identifying the Cause of Lightning**:
- The question asks for the reason behind lightning. The options provided are rain, wind, humidity, and electric discharge.

3. **Observing Thunderstorms**:
- During thunderstorms, we observe clouds that are often filled with moisture and charged particles. The presence of these clouds is crucial for the occurrence of lightning.

4. **Charge Accumulation in Clouds**:
- Within these clouds, due to various factors like friction and movement of water droplets, electrical charges accumulate. This results in some clouds becoming positively charged while others become negatively charged.

5. **Potential Difference**:
- The difference in charge between the positively charged clouds and the negatively charged clouds creates a potential difference. This is the key factor that leads to lightning.

6. **Electric Discharge**:
- When the potential difference becomes large enough, an electric discharge occurs. This discharge is what we see as lightning. It is essentially a flow of electrons from a region of higher potential (positive) to a region of lower potential (negative).

7. **Connection to Earth**:
- The Earth is considered to have zero potential. Thus, when there is a significant build-up of electrons in the clouds, the discharge can travel from the clouds to the ground, resulting in a lightning strike.

8. **Conclusion**:
- Therefore, the correct answer to the question "Lightning occurs due to" is **electric discharge**.