Arrange the following waste management practices from most sustainable to least sustainable.

1. Recycling
2. Landfilling
3. Waste-to-energy incineration
4. Composting

Explanation:

The waste management hierarchy ranks waste disposal methods based on sustainability:

1. Composting (Most Sustainable)

   • Breaks down organic waste naturally and returns nutrients to the soil.

   • Zero emissions and highly eco-friendly.

2. Recycling

   • Converts non-biodegradable materials (plastic, metal, glass, paper) into reusable products.

   • Reduces landfill waste and conserves resources.

3. Waste-to-Energy Incineration

   • Burns waste to generate electricity but releases pollutants.

   • More sustainable than landfilling but less eco-friendly than recycling.

4. Landfilling (Least Sustainable)

   • Waste is buried, leading to methane emissions, groundwater pollution, and space consumption.

   • The least environmentally friendly method.

Thus, Option (1) "4 → 1 → 3 → 2" is the correct answer.