Chalk is a C) Compound.
Element refers to one single substance which is made up of atoms and sub atomic particles namely electron, proton and neutron. A colloid is a blend where one substance of minutely scattered insoluble or solvent particles is suspended all through another substance.
Solution is composed of two components solute and solvent. When elements combine together it leads to the formation of compound. Chalk is considered as compound because, it is a substance formed by fusion of carbon dioxide and calcium hydroxide.