According to Lepcha mythology, their origins are traced to a sacred place called ‘Mayel Lyang’, which might refer to:

The correct answer is: a) A place in Sikkim.

Mayel Lyang is a sacred place in Lepcha mythology, and is believed to be the place where the Lepcha people originated. It is said to be located in the mountains of Sikkim, and is a place of great spiritual significance for the Lepcha people.

The other options are incorrect because:

• Option b) is incorrect because Tibet is not a place in Sikkim.
• Option c) is incorrect because a mythical land is not a real place.
• Option d) is incorrect because the plains of Bengal are not a place in Sikkim.

I hope this helps! Let me know if you have any other questions.