The correct answer is: a) Early nomadic hunter-gatherers.
The discovery of prehistoric tools in Meghalaya suggests the presence of early nomadic hunter-gatherers. This is because the tools are made of stone and are not very sophisticated. They are also found in areas that are not suitable for agriculture, suggesting that the people who used them were not farmers.
Option b) is incorrect because settled agricultural communities would have left behind more evidence of their presence, such as pottery and other artifacts. Option c) is incorrect because early trade routes would have been used by people who were not necessarily nomadic. Option d) is incorrect because the Bronze Age did not begin until around 3000 BC, while the tools found in Meghalaya are much older.
In conclusion, the discovery of prehistoric tools in Meghalaya suggests the presence of early nomadic hunter-gatherers.