The correct answer is: C) Sapphire.
Sapphire is a gemstone that is a variety of the mineral corundum. It is typically blue, but can also be found in other colors, such as yellow, green, orange, pink, purple, and white. Sapphire is a precious stone and is often used in jewelry.
Karnataka is a state in India that is known for its gold deposits. Gold is often found in association with other minerals, such as sapphire. Sapphire is a valuable gemstone and is often mined in Karnataka.
Ruby, emerald, and quartz are also gemstones, but they are not typically found in association with gold deposits in Karnataka. Ruby is a red gemstone that is a variety of the mineral corundum. Emerald is a green gemstone that is a variety of the mineral beryl. Quartz is a colorless or white gemstone that is a variety of the mineral silica.
Sapphire is the correct answer to the question because it is a gemstone that is sometimes found in association with gold deposits in Karnataka.