The correct option is 1 and 3 only.
Explanation
The troposphere is the lowermost layer of the atmosphere, extending to an average height of 13 km (about 8 km at the poles and 18 km at the equator). It is the most significant layer regarding atmospheric mass, weather phenomena, and life support.
- Statement 1 is correct: The troposphere contains the highest concentration of dust particles and aerosols. These solid particles are concentrated in the lower layers of the atmosphere and act as hygroscopic nuclei around which water vapour condenses to produce clouds and precipitation.
- Statement 2 is incorrect: The troposphere is not devoid of water vapour. In fact, it contains approximately 99% of the atmosphere's total water vapour. The concentration of water vapour is highest near the surface and decreases rapidly with altitude.
- Statement 3 is correct: This layer is the most important for biological activity. It contains the air necessary for respiration and is the site where all major weather phenomena (rainfall, fog, hailstorms, storms) occur, which directly influence the biosphere.
Key Takeaway: The troposphere is the densest atmospheric layer, characterized by the presence of almost all water vapour, dust particles, and weather systems essential for life.