The correct answer is C. 1970.
The Bihar State Textile Corporation Limited (BSTCL) was set up in 1970 by the Government of Bihar to promote the development of the textile industry in the state. The BSTCL has a number of mills located in different parts of Bihar, which produce a variety of textile products, including cotton yarn, fabrics, and garments. The BSTCL is a major employer in the state, and its products are sold both in India and abroad.
Option A is incorrect because the year 1901 is too early. The textile industry in India did not develop significantly until the early 20th century.
Option B is incorrect because the year 1931 is too early. The textile industry in India did not develop significantly until the early 20th century.
Option D is incorrect because the year 1985 is too late. The BSTCL was set up in 1970.