The correct answer is: a) Paleolithic Period (Old Stone Age).
The Paleolithic Period is the earliest period of human history, lasting from about 2.5 million years ago to about 10,000 years ago. During this time, humans were hunter-gatherers who lived in small groups. They used stone tools and weapons, and they lived in caves or simple shelters.
There is evidence of prehistoric human habitation in Meghalaya dating back to the Paleolithic Period. In 1974, a team of archaeologists discovered a stone tool workshop at the site of Mawmluh Cave in East Khasi Hills district. The tools found at the site date back to about 100,000 years ago. This discovery provides evidence that humans were living in Meghalaya during the Paleolithic Period.
The other options are incorrect because they are not periods of human history that correspond to the time period when humans were living in Meghalaya. The Mesolithic Period lasted from about 10,000 years ago to about 8,000 years ago. The Neolithic Period lasted from about 8,000 years ago to about 5,000 years ago. The Chalcolithic Period lasted from about 5,000 years ago to about 3,000 years ago.