Seaweeds are a source of

Options

A. chlorine
B. fluorine
C. bromine
D. iodine.

Explanation

**Step-by-Step Solution:**

1. **Understanding Seaweeds**: Seaweeds are marine algae that grow in oceans and are known for their ability to absorb various minerals and nutrients from seawater.

2. **Identifying the Elements**: The question presents four options: chlorine, fluorine, bromine, and iodine. We need to determine which of these elements seaweeds are particularly known for accumulating.

3. **Researching Seaweed Properties**: It is well-documented that certain types of seaweeds, such as kelps (e.g., Laminaria), have the ability to concentrate iodine from their environment.

4. **Iodine Accumulation**: Seaweeds can accumulate iodine at much higher concentrations than what is typically found in ocean water, making them significant sources of this element.

5. **Conclusion**: Based on the information gathered, we conclude that seaweeds are a source of iodine.

**Final Answer**: Seaweeds are a source of iodine (Option D).

---