The correct answer is A) across-the-line starters. Low horsepower, polyphase, induction motors can be started with full voltage by means of across-the-line starters. Across-the-line starters apply the full line voltage directly to the motor windings, providing maximum starting torque. This is a common and simple method for starting low horsepower induction motors. The other options are incorrect because: B) primary-resistor starters use a resistor to limit the starting current, C) compensator starters use a transformer to reduce the starting voltage, and D) autotransformer starters use a special transformer to adjust the starting voltage - these methods are more appropriate for larger induction motors that require more controlled starting.