What is the proper order, from lower purity to higher purity, of the following types of silicon? A: Metallurgical silicon / monocrystalline silicon / polysilicon B: Monocrystalline silicon / polysilicon / metallurgical silicon C: Metallurgical silicon / polysilicon / monocrystalline silicon D: Polysilicon / metallurgical silicon / monocrystalline silicon

The interface between P-type region and N-type region is called（ ）. A: the metallurgical junction B: the surface C: the junction D: the plane of port