Question

Which compound has the highest melting point?
water (H2O)
carbon dioxide (CO2), a common gas
silicon carbide (SiC), a network solid
octane (C8H18), a molecular compound

Answer 1

Think of the strength of bonds and the strength of intermolecular forces. We can eliminate CO2 and Octane due to both of them being non-polar and only experiencing London-Dispersion forces.

Answer 2

Now we are left between Water/H2O and Silicon carbide/SiC one experiences strong intermolecular forces know as Hydrogen bonding and the other is a network solid. Think of Diamond that is also a network solid and its melting point is extremely high. Now go ahead and try to understand what I wrote and pick an answer.