Water Quality and Pollution

The medium which is effected by pollutants is called as receptor.
Hence option A is correct.

Impure water contains lots of germs or bacteria. Waterborne diseases are caused by drinking contaminated or dirty water. Contaminated water can cause many types of diarrhea diseases, including cholera, and other serious illness such as gulnea worm diseases, typhoid, and dysentery.

Sewage in wastewater is released by homes, factories, industries, hospitals, offices, and other uses. These mainly occur in developing countries where people don't have access to sanitary conditions and clean water. Untreated sewage can contaminate the environment and cause disease such as diarrhoea. 

Pseudomonas putida is a gram-negative bacteria that helps in cleaning the oil spills.

Sea water is unsafe for drinking primarily because of its high salt concentration (approximately 3.5%). Drinking seawater would lead to dehydration as the body requires more water to excrete the excess salt than the water consumed. While other factors like pollution may exist, salinity is the primary reason.

River regulation includes construction of irrigation canals, ditches, drainage tunnels and damns. Though they have an immense utilization for the well-being of people, it has its own defects as it affects the natural flow of water. There will be changes in physical and chemical conditions, resulting in changes in animal and plant life of the river.

Algae have great economic importance to man as it is a rich source of protein and some algae may be used as future food apart from this, it is also true that algae enriches the soil and can be a good source to make the soil fertile. Algae are being commercially used by man in many ways. Red algae is used to produce edible gelatin. Thus, the correct answer is option D.

In addition to their ecological roles as oxygen producers and as the food base for almost all aquatic life, algae are economically important as a source of crude oil and as sources of food and a number of pharmaceutical and industrial products for humans. The taxonomy of algae is contentious and subject to rapid change as new molecular information is discovered. The study of algae is called phycology, and a person who studies algae is a phycologist.

Algae is a collective term for all those chlorophyll bearing organisms which are thalloid. So, during photosynthesis by taking in ${CO _2}$ and giving out ${O _2}$ they purify the atmosphere

Algae are primary producers that can be cultivated as a sustainable food source, which is a significant area of research for future human nutrition.

Condensation is the process where water vapor turns into liquid water. As water vapor condenses into droplets in the atmosphere, it often collects dust and other atmospheric particles, resulting in impurities.

Coliform bacteria are found in human faeces. Presence of such bacteria (E. coli is a member of the faecal coliform group) in surface water is a common indicator of faecal contamination. Sanitation program test detects the water for clearing contamination of faeces. Cholera vibrio, Salmonella typhi, Entamoeba histolytica are the pathogens found in the stagnant water or when the medical waste contaminates the water body. 

Lichen represents the symbiotic association between the algae and fungi. These absorb their mineral nutrients from the atmospheric moisture rather than the soil. So, when the air is contaminated with the sulphur oxides, they show extreme sensitivity to the toxic gas. Their existence is threatened by the oxides of sulphur in the air. The disappearance of the lichen, when exposed to the sulphur oxide, is used as bioindicator of the sulphur pollution in the air.