The change in the density of sea water is due to

Options

A. change in temperature
B. addition of fresh water
C. density is independent of external factors.
D. Both (a) and (b)

Explanation

### Step-by-Step Solution:

1. **Understanding Density**:
- Density is defined as mass per unit volume. In the case of seawater, its density can change due to various factors.

2. **Effect of Temperature**:
- The density of seawater is affected by temperature. When the temperature of seawater increases, its density decreases. This is because warmer water expands and occupies more volume, leading to lower density.
- Conversely, when the temperature decreases, the density of seawater increases until it reaches 4 degrees Celsius. Below this temperature, the density starts to decrease again due to the anomalous behavior of water.

3. **Anomalous Behavior of Water**:
- Water exhibits an unusual property where its density is highest at 4 degrees Celsius. This means that as water cools from a higher temperature to 4 degrees, its density increases. However, as it cools further below 4 degrees, its density begins to decrease again.

4. **Addition of Fresh Water**:
- The density of seawater can also change due to the addition of fresh water. Fresh water has a lower density than seawater (which contains salt). When fresh water is mixed with seawater, the overall density of the mixture will be an average of the two, leading to a change in density.

5. **Conclusion**:
- Therefore, the change in the density of seawater can be attributed to:
- Changes in temperature (affecting the density due to thermal expansion).
- The addition of fresh water (which alters the overall salinity and density).

### Final Answer:
The change in the density of seawater is due to changes in temperature and the addition of fresh water.

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