To answer this question, you need to have some knowledge about the location mentioned, Digboi in Assam, India.
Option A) Silk - This option is incorrect because Digboi in Assam, India is not known for silk production.
Option B) Gold - This option is incorrect because Digboi in Assam, India is not known for gold mining or production.
Option C) Oil - This option is correct because Digboi in Assam, India is primarily known for its oil reserves and being the site of the first oil well in Asia. Digboi has a long history of oil exploration and production.
Option D) Tea - This option is incorrect because Digboi in Assam, India is not known for tea cultivation or tea plantations.
The correct answer is C) Oil. This option is correct because Digboi in Assam, India is primarily known for its oil reserves and being the site of the first oil well in Asia.