Name a mineral element that is essential to man and can be obtained from sea weeds.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a mineral element that is essential to humans and can be obtained from seaweeds.

2. **Identifying Seaweeds**: Seaweeds are marine algae that can be classified into different groups, including Pheophyceae (brown algae), Rhodophyceae (red algae), and Chlorophyceae (green algae).

3. **Mineral Elements in Seaweeds**: Seaweeds are known to accumulate various mineral elements. Among these, certain species of Pheophyceae are particularly noted for their high mineral content.

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