Introduction:
The Seven Wonders of the Medieval World were a list of architectural marvels recognized during the Middle Ages. They were chosen for their grandeur, beauty, and historical significance. In this context, we will discuss which of the given options is not one of the Seven Wonders of the Medieval World.

Explanation:
The correct answer is option 'A' - The Great Wall of China. While the Great Wall of China is undoubtedly a remarkable feat of engineering and an iconic structure, it is not part of the Seven Wonders of the Medieval World. The list of the Seven Wonders of the Medieval World was compiled based on specific criteria and did not include the Great Wall of China. Here's a brief explanation of the other options:

1. The Leaning Tower of Pisa: Located in Pisa, Italy, the Leaning Tower of Pisa is renowned for its unintended tilt. It was constructed as a freestanding bell tower for the nearby cathedral and is considered one of the most famous landmarks in the world.

2. The Colosseum: Situated in Rome, Italy, the Colosseum is a massive amphitheater built during the Roman Empire. It was used for gladiatorial contests, public spectacles, and other events. The Colosseum is an architectural marvel and a symbol of the grandeur of ancient Rome.

3. The Taj Mahal: Located in Agra, India, the Taj Mahal is an exquisite mausoleum built by the Mughal emperor Shah Jahan in memory of his wife, Mumtaz Mahal. It is renowned for its stunning white marble construction, intricate carvings, and beautiful gardens. The Taj Mahal is considered one of the finest examples of Mughal architecture.

In conclusion, the Great Wall of China is not one of the Seven Wonders of the Medieval World. The Leaning Tower of Pisa, the Colosseum, and the Taj Mahal are three of the recognized wonders due to their historical and architectural significance.