You have three substances: #"lithium fluoride"#; #"carbon dioxide"#; and #"dinitrogen pentoxide"#. Which species should have the highest melting and boiling point?
You have 3 substances. One is ionic; and the other two are molecular..........
Ionic substances are intrinsically non-molecular, and (usually) exhibit exceptionally high melting and boiling points. And thus
But, as I have said here before, you are a physical scientist. You are required to interpret data, not to remember them. Look up the melting points/boiling points of the three substances, and see if you can interpret the data on the basis of molecularity.