Lowest equivalent resistance maximizes current

Steps:

• Current through ammeter is I = V / R_total, where V is fixed; minimize R_total for max I.
• Assume equal resistor values R; series adds resistances, parallel reciprocals sum.
• Calculate R_total: series = 3R (highest); full parallel = R/3 (lowest); mixed = between R/3 and 3R.
• Lowest R_total arrangement yields greatest I.

Why A is correct:

• A (all parallel) gives R_total = R/3 per Ohm's law, minimizing resistance and maximizing I = V / (R/3) = 3V/R.

Why the others are wrong:

• B (two parallel, one series): R_total = R + (R/2) = 1.5R > R/3, lower I.
• C (all series): R_total = 3R > R/3, much lower I.
• D (two series, one parallel): R_total = (2R || R) = (2R * R)/(3R) = (2/3)R > R/3, lower I.

Final answer: A