Dissolved oxygen in water is needed only by aquatic animals and plants . Comments.

Explanation

### Step-by-Step Solution:

1. **Understanding Dissolved Oxygen**:
- Dissolved oxygen (DO) refers to the amount of oxygen that is present in water. It is crucial for the survival of various organisms.

2. **Role of Dissolved Oxygen in Aquatic Life**:
- Aquatic animals, such as fish, rely on dissolved oxygen for respiration. They extract oxygen from water through their gills. Without sufficient DO, these organisms cannot survive.

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