B: hardness and brittleness
Explanation: Ionic compound is formed by the transfer of electrons. The ionic bond is formed between the metal and nonmetal where a metal loses electrons to form a positively charged cation and the non metal gains electrons to form negatively charged anion.
The two oppositely charged ions bound together by strong coloumbic forces and thus have high melting points, are hard and are able to dissolve in water.
The characteristic of chalk being an ionic compound is that it is hard and brittle and thus we can easily write on a chalkboard.
Hardness and brittleness
Ionic substances form crystal lattices which allow the compounds to be hard because of the strong attractions between positive and negative ions in the lattice. When pressure is applied to the compound like chalk , it may force ions of the same charge together ( i.e. positive to positive). This is called electrostatic repulsion which is able to break the crystal lattice allowing one to write on the chalkboard.
the answer is B hardness and brittleness
I did edgenuity test ;)