The correct answer is: d) Animistic traditions of the Himalayas.
The earliest inhabitants of Sikkim were the Lepchas, who are believed to have arrived in the region around 2000 BC. The Lepchas are an indigenous people who practice a form of animism, which is the belief that all living things have a soul. They believe that the spirits of the dead can influence the living, and they perform rituals to appease them.
The Lepchas were followed by the Bhutias, who arrived in Sikkim in the 13th century. The Bhutias are a Tibetan people who practice Buddhism. They brought their religion with them to Sikkim, and it has since become the dominant religion in the region.
Hinduism also has a long history in Sikkim. It was introduced to the region by the Nepalese, who began to migrate to Sikkim in the 17th century. Hinduism is now the second-largest religion in Sikkim, after Buddhism.
The Indus Valley Civilization was a Bronze Age civilization that flourished in the Indus River valley from 3300 to 1300 BC. It was one of the earliest urban civilizations in the world, and it is believed to have been the birthplace of Hinduism. However, there is no evidence that the Indus Valley Civilization had any influence on the early religious and cultural development of Sikkim.
The Buddhist traditions from the south are a reference to the Mahayana Buddhist traditions that were introduced to Sikkim from Tibet in the 17th century. These traditions have had a significant influence on the development of Buddhism in Sikkim, but they are not considered to be the original religious and cultural influences in the region.