The correct answer is: a) Advanced stone tool making techniques.
Microliths are small, thin stone tools that were used by humans in the past. They were made by chipping away at larger stones until they were the desired size and shape. Microliths were used for a variety of purposes, including hunting, fishing, and woodworking.
The presence of microliths in Arunachal Pradesh suggests that the people who lived there in the past had advanced stone tool making techniques. This is because microliths are difficult to make and require a high level of skill. The fact that microliths have been found in Arunachal Pradesh suggests that the people who lived there were skilled stone tool makers.
The other options are incorrect because they do not explain why microliths would be found in Arunachal Pradesh. Hunting and gathering lifestyle, early agricultural practices, and long-distance trade are all possible explanations for the presence of microliths in other parts of the world, but they are not supported by the evidence from Arunachal Pradesh.
In conclusion, the presence of microliths in Arunachal Pradesh suggests that the people who lived there in the past had advanced stone tool making techniques.