Blocks of magnesium are fixed to the bottom of a ship to

Options

A. block hole in the ship
B. acidity of sea water
C. make the ship lighter
D. prevent the action of water and salt

Explanation

**Step-by-Step Solution:**

1. **Understanding the Problem**: The question states that blocks of magnesium are fixed to the bottom of a ship. We need to determine the purpose of these magnesium blocks.

2. **Identifying the Material**: Magnesium is a metal that is more reactive than iron. This property is crucial for understanding its role when fixed to the bottom of a ship.

3. **Corrosion in Ships**: Ships are often made of iron or steel, which are prone to rusting when exposed to moisture and oxygen, especially in marine environments where saltwater is present.

4. **Sacrificial Anode Principle**: Magnesium acts as a sacrificial anode. This means that it will corrode (oxidize) preferentially over the iron in the ship. By doing so, it protects the iron from rusting.

5. **Conclusion**: The blocks of magnesium are used to prevent the iron parts of the ship from corroding by acting as a sacrificial metal. This ensures the longevity and structural integrity of the ship.

**Final Answer**: Blocks of magnesium are fixed to the bottom of a ship to prevent the iron from corroding by acting as a sacrificial metal.

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