Final answer:
The correct action is to clear the field and postpone the game for at least 30 minutes when lightning is seen above the playing field. The '30-minute rule' after the last observed lightning or thunder is a standard safety protocol.
Step-by-step explanation:
When an athletic trainer sees a flash of lightning above the playing field and it begins to rain, the appropriate course of action is to ensure safety for all participants and spectators. According to the National Athletic Trainers' Association (NATA) safety guidelines, play should be suspended, and the participants and spectators should seek shelter immediately in such circumstances.
The correct course of action from the given options is b. Clear the field and postpone the game for at least 30 minutes. The '30-minute rule' is commonly implemented, which dictates that from the last observed lightning or sound of thunder, there should be at least a 30-minute delay before resuming any outdoor activity. This timeframe provides some assurance that the storm is moving away instead of approaching, reducing the risk of a lightning strike. Proceeding with the game or ignoring the lightning could be highly dangerous.
It's important to note that the flash-bang ratio mentioned in other options refers to counting the seconds between the lightning flash and the sound of thunder, then dividing by five to estimate the storm's distance in miles. However, the safest practice is to clear the field immediately upon observing lightning, without waiting to measure the flash-bang ratio.