they're experts in iron metallurgy
The bantu was originated from the southern part of Africa ( round republic of Congo) , and has been the expert of utilizing iron among the ancient tribe
Mostly they use it for their Agricultural system ( such as their Irrigation system, for their agricultural tools, etc)
<span />
Matter is a slightly archaic word for something with mass, as in the conservation of matter (which must be paired with the conservation of energy to still hold true. Mass can be converted back and forth between energy, so therefore so can matter. Of course relativistic mass is conserved as it's a function of the energy of an object in that reference frame.
Doping Se (group VI elements) with P(group V)elements would produce a P-TYPE semiconductor with HIGHER conductivity compared to pure Se
the reason is P dopant will introduce holes in the Se as P has lesser valence electron