The correct answer is A) The rotational speed of the armature and the magnetic strength of the field flux. The generated voltage in a DC generator is determined by two main factors: the speed at which the armature is rotated and the strength of the magnetic field produced by the field windings. As the armature rotates through the magnetic field, it cuts across the magnetic flux lines, inducing a voltage in the armature windings. The faster the armature rotates, the greater the rate of change of the magnetic flux, and thus the higher the induced voltage. Similarly, the stronger the magnetic field, the greater the induced voltage. These two factors - rotational speed and magnetic field strength - directly determine the magnitude of the generated voltage in a DC generator. The other options are incorrect because they do not accurately describe the factors that determine the generated voltage. Option B focuses on armature current draw, which is an effect of the generated voltage, not a cause. Option C refers to the field rotation and armature flux, which are not the primary factors involved. Option D incorrectly identifies the armature current draw as a determining factor, rather than the rotational speed.