The correct answer is: c) Cuddalore.
The Neyveli Lignite Corporation (NLC) is a public sector undertaking of the Government of India. It is the largest lignite mining company in India and the third largest power generating company in the country. NLC operates three major thermal power plants in Cuddalore, Tamil Nadu. The plants have a total installed capacity of 2,400 MW.
The first option, Chennai, is incorrect because NLC does not operate any thermal power plants in Chennai. The second option, Madurai, is incorrect because NLC does not operate any thermal power plants in Madurai. The third option, Cuddalore, is the correct answer because NLC operates three major thermal power plants in Cuddalore. The fourth option, Tiruchirappalli, is incorrect because NLC does not operate any thermal power plants in Tiruchirappalli.