The correct answer is: b) Early urban settlements.
Archaeological excavations at Ambari (Guwahati) have provided evidence of early urban settlements. The site has yielded a number of artifacts, including pottery, terracotta figurines, and stone tools. These artifacts date back to the 2nd millennium BC, and provide evidence of a thriving urban civilization in the region.
The Harappan Civilization was an ancient civilization that flourished in the Indus Valley from about 2600 to 1900 BC. The Harappans were a sophisticated people who built cities, developed a system of writing, and traded with other civilizations in the region. However, there is no evidence that the Harappan Civilization extended to the Ambari region.
Pre-historic tools are tools that were made and used by humans before the development of writing. These tools can be made from a variety of materials, including stone, bone, and wood. Pre-historic tools have been found all over the world, and provide evidence of the early development of human technology. However, there is no evidence that pre-historic tools were used at the Ambari site.
Megalithic culture is a term used to describe a type of culture that is characterized by the construction of megalithic monuments. Megalithic monuments are large stone structures that were built by prehistoric peoples. These monuments can be found all over the world, and provide evidence of the early development of human culture. However, there is no evidence that a megalithic culture existed at the Ambari site.