The correct answer is: a) Pottery and bead offerings.
Prehistoric burial sites discovered in Manipur sometimes contain pottery and bead offerings. These offerings are thought to have been placed with the deceased as part of their funeral rites. The pottery is often decorated with geometric designs or animal motifs, and the beads are made from a variety of materials, including stone, glass, and shell. These offerings provide valuable insights into the beliefs and practices of the people who lived in Manipur during prehistoric times.
Option b) is incorrect because metal weapons were not commonly used in Manipur during prehistoric times. Option c) is incorrect because carved wooden figurines have not been found in prehistoric burial sites in Manipur. Option d) is incorrect because stone tools were used by people in Manipur during prehistoric times, but they were not typically placed in burial sites.