Equivalent Resistance in Series vs. Parallel Steps:

• Each resistor has resistance R; series equivalent resistance R_s = 2R.
• Series current I_s = V / 2R, where V is supply voltage.
• Parallel equivalent resistance R_p = R/2.
• Parallel current I_p = V / (R/2) = 2V/R.
• Ratio I_p / I_s = (2V/R) / (V/2R) = 4.

Why D is correct:

• Parallel combination halves the equivalent resistance compared to one resistor, quadrupling the current relative to series (by Ohm's law, I = V/R).

Why the others are wrong:

• A: 0.25 inverts the ratio, confusing current with resistance.
• B: 0.50 assumes halving resistance doubles current, ignoring series doubles resistance.
• C: 2.0 undercounts the factor from series (2R vs. R/2 is factor of 4).

Final answer: D