Which term completes the phrase: Physical, ______, biological, radiological are broad water quality categories?

• A. Chemical
• B. Thermal
• C. Microbiological
• D. Toxic

Answer: (A)

Water quality is categorized into four broad areas: physical, chemical, biological, and radiological. The blank should be filled with chemical because this category covers the chemical constituents and contaminants in water—things like minerals, metals, salts, organic compounds, nutrients, and pesticides that affect safety and taste. Physical attributes include things like temperature, turbidity, color, and taste/odor that aren’t chemical contaminants. Biological refers to microorganisms such as bacteria, viruses, and protozoa. Radiological covers radioactive substances. The other options don’t fit as the broad category here: thermal is typically considered a physical property rather than a separate category, microbiological is a more specific part of biological, and toxic describes harmful substances but isn’t used as one of the four broad categories.