(a) Solubility in water

(b) Electrical conductivity in solid-state

(c) High melting and boiling points

(d) Electrical conductivity in molten state

Solution:

Option (b) is the answer.

Because of the abundant mobile free ions in molten or solution states, ionic substances conduct electricity.

1st step:

The transport of electrons creates ionic compounds. The positively charged ion is referred to as a cation, whereas the negatively charged ion is referred to as an anion. The electric force of attraction holds them together.

2nd step:

Because hydration energy is larger than lattice energy, ionic chemicals are extremely soluble in water.

Because there are no mobile ions in ionic compounds in the solid-state, they do not conduct electricity.

Because of their high lattice energy, ionic compounds have high melting and boiling points.
In a molten or solution state, ionic compounds conduct electricity due to the presence of free ions.

3rd step:

Ionic compounds conduct electricity in the solid-state is an incorrect assertion because there are no mobile ions in the solid-state to conduct electricity.

Final step: The correct answer is (B) Solid-state electrical conductivity.