Which of the following is required by aquatic animals to breathe under water?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. Dissolved Oxygen.
Aquatic animals require dissolved oxygen to breathe underwater. This oxygen is present in water in a dissolved form, enabling fish and other aquatic organisms to extract it through specialized respiratory organs like gills. The dissolved oxygen comes from atmospheric oxygen mixing with water and photosynthesis by aquatic plants. It is essential for their survival, as it supports cellular respiration. Other gases like dissolved nitrogen, carbon dioxide, or hydrogen sulfide are not utilized for breathing and may even be harmful in high concentrations.