The correct answer is C. 2014-15.
The production of coal in Chhattisgarh increased from 102.2 million tonnes in 2012-13 to 107.3 million tonnes in 2013-14. However, it declined to 106.2 million tonnes in 2014-15. This decline was mainly due to the closure of some mines due to safety reasons.
Option A is incorrect because the production of coal increased in 2012-13 as compared to the previous year.
Option B is incorrect because the production of coal increased in 2013-14 as compared to the previous year.
Option D is incorrect because the production of coal increased in 2015-16 as compared to the previous year.
Option E is incorrect because the production of coal declined in 2014-15 as compared to the previous year.