Makaravilakku festival is celebrated at the sacred grove of Lord Ayyappa in:

Kerala 

The correct answer is Option (4) - Kerala

Makaravilakku festival is primarily celebrated at the sacred grove of Lord Ayyappa in Kerala, particularly at the Sabarimala Temple in the Pathanamthitta district of Kerala, India. This festival marks the culmination of the annual Sabarimala pilgrimage season, which typically occurs in January.