The correct answer is: d) Neolithic tools and pottery.
The Khangkhui Cave is a cave located in the Senapati district of Manipur, India. It is significant due to the discovery of Neolithic tools and pottery. The tools and pottery are made of stone and clay, and they date back to the Neolithic period. The discovery of these artifacts provides evidence of the early human habitation of the region.
The other options are incorrect. Iron Age weapons are not found in the Khangkhui Cave. Megalithic structures are large stone monuments that are found in many parts of the world. Pleistocene fossils are the remains of animals that lived during the Pleistocene epoch, which lasted from about 2.5 million to 11,700 years ago.