Identify the following substances as ionic, metallic, covalent network, or molecular solids:…

Identify the following substances as ionic, metallic,
covalent network, or molecular solids: Substance A is malleable, ductile,
conducts electricity well, and has a melting point of 1135 °C. Substance B is
brittle, does not conduct electricity as a solid but does when molten, and has
a melting point of 2072 °C. Substance C is very hard, does not conduct
electricity, and has a melting point of 3440 °C. Substance D is soft, does not
conduct electricity, and has a melting point of 185 °C.