The correct answer is: a) Rangpur.
Rangpur is a Chalcolithic archaeological site located in the district of Amreli in Gujarat, India. It is one of the most important Chalcolithic sites in Gujarat, and has been dated to the period between 2500 and 1500 BCE. The site is known for its well-preserved remains of a settlement, including houses, pottery, and copper tools.
The Chalcolithic Era is a period of prehistory that saw the development of copper metallurgy. This era is particularly evident at the Rangpur site, where copper tools and weapons have been found in abundance. The use of copper at Rangpur suggests that the inhabitants of the site were skilled metalworkers.
The other options are incorrect because they are not Chalcolithic sites. Prabhas Patan is a Hindu pilgrimage site, Girnar is a mountain range, and Junagadh is a city.