Correct Option
The correct option is (c).
Explanation
The circulation of air in the atmosphere is primarily driven by the uneven heating of the Earth's surface. This process involves changes in air temperature, density, and pressure, leading to the formation of convection currents.
Statement-wise Analysis
- Statement 1 is Incorrect. When air is heated, its molecules gain energy and move apart, causing the air to expand. Consequently, it becomes lighter (less dense) and rises, rather than contracting or becoming heavier.
- Statement 2 is Correct. Cold air has molecules that are packed more closely together, making it denser and heavier than warm air. Due to this higher density, cold air tends to sink towards the Earth's surface, creating areas of high pressure.
- Statement 3 is Correct. As warm air rises, it creates a region of low pressure or a "gap" near the surface. Cold air from surrounding high-pressure areas rushes in to fill this space. This continuous movement of air sets up air circulation patterns (winds).
Key Takeaway
Air Circulation Principle: Warm air expands, becomes lighter, and rises (Low Pressure), while cold air contracts, becomes denser, and sinks (High Pressure). Wind is the movement of air from high pressure to low pressure to replace rising warm air.