Answer
Please see the work below.
Work Step by Step
We know that
a. $CO_2$ has discrete nopolar molecules which are held together int he solid by weak dispersion forces.$SiO_2$ is a covalent network solid.
b. $HF$ has a strong hydrogen bonding while $HCl$ has weak hydrogen bonding comparatively that's why it boils at low temperature.
c. $SiF_4$ is a large molecule that's why it has stronger dispersion forces and a higher boiling pint as compared to $CF_4$.
