The correct answer is: b) Leather.
Leather is the main material used in making traditional Sikkimese boots. The boots are often decorated with colorful patterns, which are made by hand using a variety of techniques. The boots are typically made from the skin of yaks, cows, or goats. They are then dyed and decorated with patterns that are often inspired by nature. The boots are typically worn by both men and women in Sikkim. They are often worn for special occasions, such as weddings and festivals.
The other options are incorrect. Clay is not typically used in making traditional Sikkimese boots. Metal is sometimes used in making the soles of the boots, but it is not the main material used. Stone is not used at all in making traditional Sikkimese boots.