A is an ionic structure and bonding, giant ionic lattice, high melting/boiling point, only conducts when molten, the solubility and electrical conduction in water is extra evidence, but isn't definitive for substance A (see E).

Typical examples would be salts like sodium chloride, magnesium sulfate

B is a giant metallic lattice structure and metal bonds, high melting/boiling points, high density, conducts in solid, not just liquid.

Typical examples would be iron and copper.

C simple molecular structure, small molecules with covalent bonds, low melting/boiling point, no electrical conduction at all (no ions).

Typical examples would organic compounds like waxes which dissolve in organic solvents like hexane or propanone ('acetone').

D giant covalent lattice, very high melting/boiling, no electrical conduction, won't dissolve in anything.

Typical examples are carbon (diamond), silicon, silicon dioxide (silica) and many other minerals found in rocks.

I've made A to D quite straightforward (as long as Bonding Parts 2 to 5 have been studied), but I've

E simple molecular structure, small molecules with covalent bonds, low melting/boiling point, no electrical conduction when molten, however it does conduct when dissolved in water, so ions must be formed to conduct electricity. The latter is a 'red herring', if it had an ionic structure the melting/boiling points would be much higher and the liquid would have conducted.

Examples are the gases hydrogen fluoride, hydrogen chloride, hydrogen bromide and hydrogen.

These are all simple molecular substances, diatomic covalent molecules HF, HCl, HBr, HI), BUT they dissolve in water to form acids solutions containing the hydrogen ion (H⁺) and the corresponding halide ion (F^–, Cl^–, Br^–, I^–), hence the reason why the aqueous solution conducts electricity. Small covalent molecules often dissolve in organic solvents.

F Probably a thermally very stable giant covalent structure, but with weakly electrical conducting properties (even in the solid) due to delocalised electrons, completely insoluble. Its unlikely to be an ionic structure because it conducts in the solid. Metals do not decompose on heating to a high temperature and all metals will boil.

Examples might be carbon (graphite) and nanomaterials derived from carbon