KF being highly ionic compound will dissolve most readily in water. (Like disolves like).

Higher the difference in electronegativity between the two atoms, more will be electrovalent character of the bond. Among given choices, calcium and hydrogen have maximum difference in their electronegativities.

So, in CuSO₄.5H₂O one electrovalent bond, 5 coordinate bonds and covalent bonds are present.

The strength of a bond depends upon the extent of overlapping. s-s and s-p overlapping results in the formation of ?-bond but extent of overlapping along inter nuclear axis is more in case of s-s overlapping than in s-p. p-p overlapping may result in ?-bond if overlapping takes place along inter nuclear axis or may result in ?–bond if sideways overlapping takes place.In any case the extent of overlapping is lesser in p - p than that of the other two,s - s and s-p.Hence the correct order is s - s > s - p > p - p.

In KCN, K⁺ and CN^- have ionic bond and C ≣ N has covalent bond.

For compounds containing cations of same charge,lattice energy increases as the size of the cation decrease. Thus, NaF has highest lattice energy. The size of cations is in the order Na⁺ < K⁺ < Rb⁺ < Cs⁺.

The stability of the ionic bond depends upon the lattice energy which is expected to be more between Mg and F due to +2 charge on Mg atom.

Dative bond is formed between two atoms when the electrons of shared pair are contributed solely by one of the two atoms and it is directed toward that atom which do not contribute the electrons. It is represented by an arrow on the bond which is directed towards the electron recipient atom.

So, –N⁺ ≣ NCl^- is the only group among the given options which does not contain a dative bond.