Answer:
Due to electrostatic force
Gold! it's boiling point is 2807 according to this chart:
http://www.lenntech.com/periodic-chart-elements/boiling-point.htm
I would choose C bc if u look at it closely u can notice it goes up steadily and then BANG it decreases a lot
Ba3PO4 is not neutral, it is positive. (NH4)2SO4 is neutral, the charges cancel.
Mg2OH is not neutral, it is positive. LiF2 is not neutral, it is negative. CaOH is not neutral, it is positive. The answer is (NH4)2SO4, correct ions will have a neutral charge.