Parallel cells extend battery life Steps:

• Assume diagram shows three 1.5V cells connected in parallel, as total e.m.f. remains 1.5V.
• In parallel, voltage equals single cell (1.5V), but internal resistance decreases to one-third.
• Total capacity (ampere-hours) triples compared to one cell.
• For same load current, discharge time extends proportionally to capacity.

Why A is correct:

• Parallel connection sums charge capacities (Q = n × Q_single, where n=3), allowing longer current supply per Faraday's law of electrolysis or basic battery runtime formula t = Q/I.

Why the others are wrong:

• B: Parallel fixes e.m.f. at 1.5V; no variable output without switching.
• C: E.m.f. per coulomb stays 1.5V, same as single cell (work per charge = V).
• D: Parallel e.m.f. is 1.5V, not additive to 4.5V (that's series).

Final answer: A