2. 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.