Answer:
a, b and c
Step-by-step explanation:
A - Ionic compounds have ionic bonds which are far more stronger than the intermolecular forces in molecular (covalent) compounds, so more energy is required to break the bonds, this having a higher boiling point
B - when ionic compounds are placed in water, they are attracted to water due to its dipole nature, so the water molecules attract the positive and negative ions from the compound, breaking the ions apart in a process called dissociation
C - NaCl is an ionic compound as it consists of a metal (Na) and a non-metal (Cl) where Na loses an electron to form +1 ion and Cl gains that electron to form -1 ion. It is poor in conducting electricity when it is in the solid state as the ions are held in fixed positions and cannot move. They can only conduct electricity when molten or dissolved in solution as the ions are free to move around.
D - The first part of the sentence is right : The overall charge of an ionic compound has to be zero as the positive and negative ions are equal, which maintains its neutrality. In general, most compounds have good solubilty in water as water molecules are polar they can attract the positive and negative ions and break up the structure.
There are a few exceptions, for example ionic compounds that have highly polarising ions (are small and have a high charge) which water is unable to break apart the ions.