The correct answer is (a) Behdienkhlam.
Behdienkhlam is a major festival of the Khasis, an ethnic group in Northeast India. It is a time for ancestor worship and thanksgiving. The festival is held in the month of November, and it lasts for three days.
On the first day of the festival, the Khasis offer sacrifices to their ancestors. They also pray for good health and prosperity. On the second day, the Khasis dance and sing. They also play traditional games. On the third day, the Khasis feast and celebrate.
The festival is a time for the Khasis to come together and celebrate their culture. It is also a time for them to remember their ancestors and to give thanks for all that they have.
The other options are incorrect because they are not associated with ancestor worship and thanksgiving.
(b) Nongkrem Dance is a dance performed by the Khasis to celebrate the harvest.
(c) Wangala is a festival of the Khasis that is held to celebrate the beginning of the new year.
(d) Chapchar Kut is a festival of the Khasis that is held to celebrate the end of the harvesting season.