The correct answer is B) 110 volts. The explanation is as follows: 1. The turns ratio of the step-down transformer with dual voltage secondary is two to one (total). This means that the secondary windings have half the number of turns as the primary winding. 2. Since the primary voltage is 440 volts, and the turns ratio is 2:1, the secondary voltage will be 440 / 2 = 220 volts. However, the secondary windings are connected in parallel, so the measured voltage across 'X1-X3' and 'X2-X4' will be 220 volts divided by 2, which equals 110 volts. 3. The other options are incorrect because 55 volts (A) is half of the correct answer, 220 volts (C) is the voltage of the individual secondary windings, and 880 volts (D) is twice the primary voltage, which is not the correct secondary voltage.