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Monosodium glutamate (MSG) is a flavor enhancer commonly added to Chinese food, canned vegetables, soups and processed meats.

Relative to metals, glass is a poor conductor of heat. It is a better heat conductor than some other common building materials, such as wood.

Bleaching liquor, which often contains chlorine-based compounds, is a significant byproduct and pollutant generated during the bleaching processes in the paper and pulp industry. Cellulose fibers and drugs are products rather than pollutants in the context of their respective industries. Thus, pairing 'a' is the only accurate association provided in the options.

Alum, typically potassium aluminum sulfate, is used in water treatment as a flocculant. It neutralizes the negative charges of suspended colloidal particles, allowing them to aggregate into larger particles called flocs, which can then be easily removed by filtration or sedimentation.

Water is considered a cyclic resource because it moves continuously through the Earth's environment via the hydrological cycle. This process involves evaporation, condensation, and precipitation, ensuring that water is constantly recycled and redistributed across the planet's surface and atmosphere.

Bleaching powder, or calcium hypochlorite, releases chlorine when dissolved in water. Chlorine is a potent oxidizing agent that kills bacteria, viruses, and other microorganisms, effectively acting as a disinfectant to make water safe for human consumption. It is a standard treatment method in municipal water purification systems worldwide.

Biodegradable waste refers to organic matter that can be broken down by microorganisms into simpler substances. Wool is a natural protein fiber derived from sheep, making it biodegradable. In contrast, nylon, plastic, and polythene are synthetic polymers that persist in the environment for very long periods because they lack natural enzymatic pathways for degradation.

The discharge of industrial and domestic effluents into water bodies introduces various chemical pollutants, heavy metals, and organic matter. These substances significantly alter the pH, dissolved oxygen levels, turbidity, and overall chemical composition of the water, leading to pollution and degradation of aquatic ecosystems.

Eutrophication is the process where a water body becomes overly enriched with minerals and nutrients, particularly nitrogen and phosphorus compounds. These nutrients, often derived from agricultural runoff or sewage, stimulate excessive growth of algae and aquatic plants. While this leads to oxygen depletion, the root cause of the phenomenon is the influx of these specific nutrients.