The correct answer is c) Thiruvananthapuram.
Amethyst and aquamarine are occasionally found in the state of Kerala, India. The most famous gem mine in Kerala is the Pazhayar mine, which is located in the Thiruvananthapuram district. The Pazhayar mine has been in operation for over 200 years and is known for its high-quality amethyst and aquamarine.
The other options are incorrect because they are not located in the state of Kerala. Thrissur is a city in the state of Kerala, but there are no gem mines in the city. Palakkad is a district in the state of Kerala, but there are no gem mines in the district. Ernakulam is a city in the state of Kerala, but there are no gem mines in the city.
Amethyst is a purple variety of quartz. It is a semi-precious gemstone that is often used in jewelry. Aquamarine is a blue-green variety of beryl. It is a semi-precious gemstone that is often used in jewelry.