The calm and dark back part of the moon is called

Options

A. sea of tranquility
B. oceans of storms
C. Both (A) and (B)
D. None of these

Explanation

**Step-by-Step Solution:**

1. **Understanding the Moon's Visibility**: The moon is a celestial body that orbits the Earth. It is important to note that only about 57% of the moon's surface is visible from Earth at any given time. The rest of the moon is not visible due to its synchronous rotation with the Earth.

2. **Identifying the Dark Side**: The part of the moon that is not visible from Earth is often referred to as the "dark side." However, this term can be misleading because both sides of the moon receive sunlight; it's just that one side is always facing away from the Earth.

3. **The Calm and Dark Back Part**: The specific term for the calm and dark back part of the moon is "Sea of Tranquility." This area is known for its smooth, flat plains and is one of the most famous lunar maria.

4. **Apollo 11 Landing**: The Apollo 11 mission was the first manned mission to land on the moon. It landed in the Sea of Tranquility, which is why this area is often highlighted in discussions about lunar exploration.

5. **Conclusion**: Therefore, the calm and dark back part of the moon is called the "Sea of Tranquility."

**Final Answer**: Sea of Tranquility

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