Question

what is the primary role of dissolved oxygen in water for aquatic life?
allows for better water navigation
provides all nutrients for life
to allow aquatic animals to breathe
to support all photosynthesis

Explanation:

Aquatic animals, like fish, use gills to extract dissolved oxygen from water for respiration. Dissolved oxygen is crucial for their survival as it is used in the process of cellular respiration to release energy. The other options are incorrect: dissolved oxygen does not aid in water navigation (that's more about body structure and senses), it does not provide all nutrients (nutrients come from various sources like food), and it is not directly related to supporting all photosynthesis (photosynthesis in aquatic plants mainly uses carbon dioxide and sunlight).

Answer:

to allow aquatic animals to breathe