The upper part of sea water mainly contains

Options

A. Nektons only
B. Planktons only
C. Nektons and planktons both
D. None of the above

Explanation

To answer the question about what the upper part of sea water mainly contains, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Components of Marine Life**:
- Marine life can be categorized into three main groups:
- **Plankton**: These are organisms that drift in the water and cannot swim against currents. They are typically found in the upper layers of the ocean.
- **Necton**: These are actively swimming organisms, such as fish and marine mammals, that can move independently of water currents.
- **Bentos**: These organisms live on or near the sea floor and are not found in the upper layers of the water.

2. **Identifying the Location of Each Group**:
- Since the question specifically asks about the upper part of sea water, we need to focus on the organisms that inhabit this region.
- **Plankton** is primarily found in the upper layers as they float and drift with the water currents.
- **Necton** is also found in the upper part of the sea as they swim actively in these layers.

3. **Eliminating Incorrect Options**:
- **Bentos** can be eliminated because they are located at the bottom of the sea and not in the upper part of the water column.
- The options provided include:
- Nectons only
- Plankton only
- Nectons and plankton both
- None of the above
- Since both plankton and necton are present in the upper part of the sea, the option that includes both is the correct answer.

4. **Conclusion**:
- The upper part of sea water mainly contains both **nectons and plankton**.

### Final Answer:
The upper part of sea water mainly contains **nectons and plankton both**.

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