Final answer:
The statement is false; in the BOTH position, the magnetos are not grounded but are both active to ensure redundancy in an aircraft's ignition system.
Step-by-step explanation:
The statement is false. In the BOTH position for an aircraft's ignition system, the right and left magnetos are not grounded; both are active to provide redundancy. The OFF position would ground both magnetos, stopping the engine. Magnetos are part of an aircraft's ignition system, and grounding a magneto disables it, preventing it from generating the spark needed for ignition in the spark plugs of an engine.