Identify the inorganic impurity category among the following common pollutants found in contaminated water.

Introduction:
Water pollution contains both organic and inorganic components. Distinguishing these classes helps select appropriate treatment processes.

Given Data / Assumptions:

• We compare typical pollutant classes.
• Focus is on identifying an inorganic impurity.
• General environmental engineering context.

Concept / Approach:
Organic compounds contain carbon-hydrogen frameworks (e.g., fats, carbohydrates, proteins). Inorganics include minerals, salts, and metals that do not fit typical organic structures.

Step-by-Step Solution:
Step 1: Classify each option as organic or inorganic.Step 2: Fats, carbohydrates, and proteins are organic.Step 3: Salts of metals are inorganic species.Step 4: Therefore, salts of metals are the inorganic impurities.

Verification / Alternative check:
Common inorganic ions include chlorides, sulfates, nitrates, and metal cations, all requiring different treatment than organics.

Why Other Options Are Wrong:
Fats, carbohydrates, proteins, and natural oils are carbon-based organics and do not represent inorganic impurities.

Common Pitfalls:
Assuming “natural” equals “inorganic.” Many natural substances are organic.

Final Answer:
Salts of metals