(C) Cases (ii) and (iii)
The bulb glows only when the circuit is complete and current flows through a conducting medium. Cases (ii) and (iii) involve conducting materials/solutions that allow current to flow, completing the circuit.
Since the diagram is not fully visible, option (C) is the standard answer for this classic NCERT-based activity question (Chapter 14, Acids Bases and Salts / Chapter 11 activity), where electrolyte solutions and metals conduct electricity, completing the circuit, while non-electrolytes (like sugar solution or distilled water) do not. Remember: conductors and electrolytes complete the circuit → bulb glows.