The correct answer is option 'A', Everest.

Everest, also known as Mount Everest, is the highest mountain peak on Earth. It is located in the Mahalangur Himal sub-range of the Himalayas and straddles the border between Nepal and China (Tibet Autonomous Region). Here is a detailed explanation of why Everest is the highest mountain peak:

1. Elevation:
- Everest has an elevation of 8,848.86 meters (29,031.7 feet) above sea level, making it the highest point on Earth.
- The elevation was determined by a survey conducted by the Survey of India in 1955, and it has been widely accepted since then.

2. Himalayas:
- The Himalayas are the world's highest mountain range, stretching across several countries including Nepal, India, China, Bhutan, and Pakistan.
- Everest is part of the Mahalangur Himal sub-range of the Himalayas, which is known for its towering peaks.
- The Himalayas were formed by the collision of tectonic plates, pushing the Earth's crust upward and creating these majestic mountains.

3. Geological Formation:
- Everest is primarily composed of sedimentary and metamorphic rocks, including limestone, marble, and schist.
- The peak was formed through the process of tectonic uplift, where the Indian subcontinent collided with the Eurasian Plate, causing the Himalayas to rise.

4. Climbing and Expeditions:
- Everest has been a popular destination for mountaineers since the early 20th century.
- The first successful ascent of Everest was made by Sir Edmund Hillary of New Zealand and Tenzing Norgay, a Sherpa of Nepal, on May 29, 1953.
- Since then, thousands of climbers have attempted to reach the summit, with varying degrees of success.

5. Climate and Conditions:
- Climbing Everest is an extremely challenging and dangerous feat due to its extreme weather conditions, low temperatures, high winds, and low oxygen levels.
- The region is known for its unpredictable weather patterns, and climbers must be well-prepared and experienced to tackle the mountain.

In conclusion, Mount Everest is the highest mountain peak on Earth due to its impressive elevation, its location in the Himalayas, and its geological formation. Climbing Everest is a remarkable achievement and requires extensive preparation, skill, and determination.