The correct answer is: A. Cassiterite.
Cassiterite is the primary ore of tin. It is an oxide mineral with the chemical formula SnO2. Cassiterite is a black or brown mineral that is typically found in veins or lodes. It is the most important source of tin, which is used in a variety of applications, including tin plating, solder, and bronze.
Wolframite is an iron-manganese tungstate mineral with the chemical formula (Fe,Mn)WO4. Wolframite is a black or brown mineral that is typically found in veins or lodes. It is the primary ore of tungsten, which is used in a variety of applications, including high-speed steel, cemented carbides, and light bulbs.
Hematite is an iron oxide mineral with the chemical formula Fe2O3. Hematite is a red, brown, or black mineral that is typically found in igneous and metamorphic rocks. It is the most common iron ore and is used in a variety of applications, including steelmaking, iron casting, and pigments.
Therefore, the correct answer is A. Cassiterite.