The correct answer is A. contamination by human wastes.
Coliform bacteria are a group of bacteria that are found in the intestines of warm-blooded animals. They are usually harmless, but some types can cause illness, especially in people with weakened immune systems. Coliform bacteria are often used as an indicator of water quality, because their presence indicates that the water may be contaminated with human or animal waste.
Phosphorus is an essential nutrient for plants, but it can also cause problems in water. When too much phosphorus is present in water, it can lead to the growth of algae blooms. Algae blooms can block sunlight from reaching other plants and animals, and they can also produce toxins that can harm people and animals.
Biological Oxygen Demand (BOD) is a measure of the amount of oxygen that is used up by bacteria as they break down organic matter in water. High BOD levels can indicate that the water is polluted with organic matter, which can lead to problems for fish and other aquatic life.
Hydrocarbon contamination is caused by the presence of oil or other hydrocarbons in water. Hydrocarbons can come from a variety of sources, including oil spills, leaks from underground storage tanks, and runoff from roads and parking lots. Hydrocarbon contamination can cause a number of problems, including fish kills, damage to aquatic ecosystems, and human health problems.