The correct answer is (a) Main Boundary Thrust (MBT).
The Main Boundary Thrust (MBT) is a major thrust fault in the Himalayas that separates the Lesser Himalaya from the Greater Himalaya. It is a reverse fault, meaning that the hanging wall (the block of rock above the fault) has moved up relative to the footwall (the block of rock below the fault). The MBT is a major tectonic boundary, and it has played a significant role in the formation of the Himalayas.
The MBT is a complex fault, and it is not well-defined in all places. It is generally located at the base of the Lesser Himalaya, but it can be found at higher elevations in some places. The MBT is a major source of seismicity in the Himalayas, and it has been the site of several large earthquakes.
The MBT is a significant geological feature, and it is important for understanding the geology of the Himalayas. It is also a popular tourist destination, and it is possible to hike along the MBT in some places.
The other options are incorrect.
(b) The Trans Himadri Thrust is a thrust fault that separates the Greater Himalaya from the Tibetan Plateau.
(c) The Main Central Thrust is a thrust fault that separates the Lesser Himalaya from the Greater Himalaya.
(d) The Almora Thrust is a thrust fault that separates the Lesser Himalaya from the Siwalik Hills.