The main mineral of tungsten is

The correct answer is A. wolframite.

Wolframite is a mineral that is composed of tungsten and iron. It is the main ore of tungsten, which is a metal that is used in many industrial applications, such as in the manufacture of light bulbs, electronics, and tools.

Hematite is a mineral that is composed of iron oxide. It is the most common iron ore, and it is used in the manufacture of steel.

Magnetite is a mineral that is composed of iron oxide and oxygen. It is a naturally occurring magnet, and it is used in the manufacture of magnets and other magnetic devices.

None of these is the main mineral of tungsten.