The metal which is obtained from both sea-water and ore from the earths solid crust is

Options

A. Magnesium
B. Copper
C. Silver
D. Calcium

Explanation

To solve the question, "The metal which is obtained from both sea-water and ore from the earth's solid crust is," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: We need to identify a metal that can be sourced from both seawater and from ores found in the earth's crust.

2. **Identify Metals in Seawater**: Seawater contains various dissolved salts, including magnesium chloride (MgCl2). This indicates that magnesium can be extracted from seawater.

3. **Identify Ores in the Earth's Crust**: Next, we need to consider which ores contain magnesium. One of the common ores of magnesium is carnallite (KMgCl3·6H2O), which is found in the earth's crust.

4. **Confirm the Metal**: Since magnesium can be obtained from both seawater (as MgCl2) and from its ore (carnallite), we conclude that magnesium is the metal that fits the criteria of the question.

5. **Final Answer**: Therefore, the metal which is obtained from both seawater and ore from the earth's solid crust is **magnesium**.