Which of the following substances has the highest melting point?

In silicon dioxide $(SiO_2)$,what is the structural arrangement of atoms?

The hydration energies of $K^{+}$ and $Cl^{-}$ are $-x$ and $-y$ $kJ / mol$ respectively. If the lattice energy of $KCl$ is $-z$ $kJ / mol$,then the heat of solution of $KCl$ is $:$

In silicon dioxide $(SiO_2)$:

Carbon dioxide is a gas,while $SiO_2$ is a solid because

Arrange the following forces in the increasing order of their interaction energy:
London forces,Covalent bond,Hydrogen bond,Dipole-dipole forces