Question about year 11 chemistry- ionisation"

For the following question:
12. Select the equation which represents an ionisation reaction with water.
A. NaCl(s) → Na+(aq) + Cl-(aq)
B. CuBr2(s) → Cu2+(aq) + 2Br-(aq)
C. HBr (g) → H+(aq) + Br-(aq)
D. PbBr2(s) → Pb2+(aq) + 2Br-(aq)


why is C the right answer and not the others?

Nowadays the terms "ionization reaction" and "dissociation reaction" are often used interchangeably. But for the purist, reactions A, B, and D should be called dissociation reactions because they involve the separation of the ions in ionic compounds as they dissolve in water. Reaction C, on the other hand, involves a covalent compound forming ions as it dissolves, and is properly called an ionization reaction.
The ionic compounds already had ions, which dissociated. HBr, a covalent compound, reacted with water to form ions - it ionized.