Step 1: Understanding the Concept:
Green chemistry promotes the use of safe, non-toxic, and environmentally friendly solvents.
Step 2: Key Formula or Approach:
Avoid VOCs (Volatile Organic Compounds) and halogenated solvents.
Step 3: Detailed Explanation:
- $\text{CH}_2\text{Cl}_3$ (typo in image, likely $\text{CH}_2\text{Cl}_2$), $\text{CHCl}_3$ (Chloroform), and $\text{CCl}_4$ are all halogenated organic solvents. They are toxic, hazardous to the ozone layer, and pollute the air and water.
- Water ($\text{H}_2\text{O}$) is a non-toxic, non-flammable, and abundant natural solvent. Using water as a reaction medium is a key strategy in green chemistry to minimize waste and pollution.
Step 4: Final Answer:
$\text{H}_2\text{O}$ is the solvent used to avoid waste and air pollution.