Answer:
brittle
Step-by-step explanation:
Option A is correct. Solid ionic crystals exist in crystal lattice with oppositely charged ions packed against each other in a repetitive manner. Mechanical stress causes similar charged ions to slide past each other generating a lot of repulsive force thus breaking the crystal making them brittle.
Option B is incorrect as solid ionic crystals have high melting point. Covalent compounds have low melting point.
Option C is incorrect. Solid ionic crystals are hard not soft this is because of the crystal lattice structure. Amorphous solids are soft.
Option D is incorrect. Solid ionic crystals are poor conductors of electricity. They conduct electricity when molten (fused) or dissolved in water so that they can split into ions that can conduct electricity.