Which of the following retards the self purification of stream? A. Higher temperature B. Sunlight C. Satisfying oxygen demand D. None of the above

The correct answer is A. Higher temperature.

A higher temperature can retard the self purification of a stream because it increases the rate of chemical reactions, including those that break down organic matter. This can lead to a decrease in dissolved oxygen levels, which can harm aquatic life.

Sunlight is necessary for photosynthesis, which produces oxygen. Therefore, sunlight can help to improve the self purification of a stream.

Satisfying oxygen demand means that there is enough oxygen in the water to support aquatic life.

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