It is commonly believed that the earth's magnetism is due to the :

Options

A. presence of a huge permanent magnet in the interior of the earth
B. pressure of electric currents circulating in the interior of the earth
C. influence of sun's magnetic field
D. influence of a nuclear explosion

Explanation

To solve the question regarding the cause of Earth's magnetism, we need to analyze the provided options one by one and determine which one is correct.

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the reason behind Earth's magnetism. We have four options to consider.

2. **Evaluate Option 1**:
- **Presence of a huge permanent magnet in the interior of the earth**:
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