The correct answer is a) Thiruvananthapuram.
Lignite is a type of coal that is less mature than bituminous coal and anthracite. It is found in sedimentary rocks and is formed from the remains of plants that have been buried and subjected to heat and pressure over millions of years. Lignite is a soft, brown coal that has a high moisture content. It is used as a fuel for power plants and in the production of chemicals.
Lignite deposits have been discovered in certain areas of Thiruvananthapuram district in Kerala. The deposits are located in the Neyyar and Karamana river valleys. The lignite is of low quality and is not suitable for use as a fuel. However, it can be used in the production of chemicals.
The other options are incorrect.
Option b) Alappuzha is a district in Kerala that is not known for its lignite deposits.
Option c) Kannur is a district in Kerala that is known for its iron ore deposits.
Option d) Kozhikode is a district in Kerala that is known for its coffee and spices.