The correct answer is: a) Shivalik Hills region.
The Shivalik Hills are a mountain range in northern India and Pakistan. They are a sub-range of the Himalayas and are located to the south of the main Himalayan range. The Shivalik Hills are a major source of sediment for the Indus River and are home to a variety of plant and animal life.
Prehistoric stone tools have been found in the Shivalik Hills region of Punjab. These tools date back to the Paleolithic period and are evidence of early human habitation in the region. The tools are made from a variety of materials, including flint, chert, and quartz. They are typically handaxes, cleavers, and scrapers.
The Shivalik Hills region is a good place to find prehistoric stone tools because it is a geologically active area. The mountains are constantly being eroded, which exposes new layers of rock. These layers of rock often contain fossils and artifacts, including prehistoric stone tools.
The other options are incorrect because they are not areas where prehistoric stone tools have been found. The Plains of central Punjab are a fertile agricultural region. The Indus River Valley is a major river valley in Pakistan. The Thar Desert border is a desert region in India and Pakistan.