discrete molecules?

The answer is B.

The term "discrete molecules" means "separated molecules". In reading the question, the word "discrete" could be neglected.

(1) is incorrect.
Graphite has giant covalent structure, in which carbon atoms are held together by a network of strong covalent bonds. Therefore, graphite does NOT exist as discrete molecules.

(2) is correct.
Bromine has simple molecular structure, in which the Br2 molecules are held together by weak van der Waals' forces.

(3) is correct.
Pure hydrogen chloride has simple molecular structure, in which HCl molecules are held together by weak van der Waals' forces.
(Note that H+ and Cl- are formed only when HCl is dissolved in water.)

(4) is incorrect.
Calcium chloride has giant ionic structure, in which calcium ions and chloride ions are held together by strong electrostatic forces. Therefore, calcium chloride does NOT exist as discrete molecules.
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