Diode conduction minimizes effective resistance for maximum battery current

Steps:

• Determine diode states: forward-biased diodes conduct (0 Ω), reverse-biased block (∞ Ω).
• Identify active paths and compute equivalent resistance (R_eq) using series/parallel rules for conducting elements.
• Calculate battery current I = V / R_eq, where V is battery voltage; identical batteries mean highest I for lowest R_eq.
• Compare R_eq across circuits to find minimum.

Why A is correct:

• Both diode branches conduct in parallel, yielding R_eq = R/2 per Ohm's law for parallel resistors, minimizing load.

Why the others are wrong:

• B: One diode blocks, leaving single series path with R_eq = 2R, higher than A.
• C: Diodes create series opposition, R_eq = 3R, even higher resistance.
• D: Reverse diode blocks main path, R_eq ≈ ∞, negligible current.

Final answer: A