The tiny free-swimming animals on the surface of water constitute

Options

A. (a) phytoplankton
B. (b) nekton
C. (c) benthon
D. (d) zooplankton

Answer

To solve the question regarding the tiny free-swimming animals on the surface of water, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks about tiny free-swimming animals that are found on the surface of water. We need to identify the correct term that describes these organisms.

2. **Identify Key Terms**: The phrase "free-swimming" indicates that these animals move with the water currents, and "on the surface of water" specifies their habitat.

3. **Consider the Options**: The options typically include terms like plankton, nekton, and benthos. We need to analyze each of these terms to find the one that fits the description.

4. **Define Plankton**: Plankton consists of small organisms that float or drift in water. They are categorized into two main groups:
- **Phytoplankton**: Plant-like organisms that can photosynthesize.
- **Zooplankton**: Animal-like organisms that are typically free-swimming and can be found near the surface of water.

5. **Define Nekton**: Nekton refers to larger aquatic animals that can swim against water currents, such as fish, sharks, and dolphins. They are not limited to the surface and are generally larger than plankton.

6. **Define Benthos**: Benthos are organisms that live on or in the bottom of water bodies. They include sponges, corals, and crabs, which do not fit the description of free-swimming animals at the surface.

7. **Select the Correct Answer**: Since the question specifies "tiny free-swimming animals on the surface of water," the correct answer is **zooplankton**. They are small, free-floating animals that inhabit the surface waters.

### Conclusion:
The tiny free-swimming animals on the surface of water constitute **zooplankton**.

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