Which of the following are indicators of water quality?

Water quality indicators are critical parameters that reflect the health of water bodies and their ability to support aquatic life and recreation. The selection of pH levels, dissolved oxygen, bacteria counts, and temperature as indicators represents a comprehensive approach to assessing water quality.

pH levels indicate the acidity or alkalinity of water, which can affect the solubility of nutrients and toxins, impacting aquatic organisms. Dissolved oxygen is essential for the survival of fish and other aquatic life; low levels can signify pollution or excessive organic matter decomposition. Bacteria counts, particularly coliform bacteria, are used to evaluate the safety of water for human consumption and recreation, as high counts can indicate fecal contamination and increased health risks. Water temperature affects many chemical and biological processes, influencing the growth rates of plants and fish, as well as the overall ecosystem dynamics.

In contrast, air temperature and humidity, types of vegetation, soil composition, and wildlife population counts, while valuable ecological indicators, do not directly measure water quality. They may have indirect effects or correlations with water quality but do not serve as primary metrics for evaluating the condition of water bodies themselves. Thus, the inclusion of specific water quality parameters in option B makes it the most accurate choice for assessing the health of aquatic ecosystems.