What is the ruling regarding the use of an electric heater in the dugout for warming bats?

The ruling states that the use of artificial means, such as an electric heater, for temperature control in the dugout is prohibited. This is aligned with the rules that aim to maintain fairness and integrity during the game. The intent behind this regulation is to prevent teams from gaining an unfair advantage by artificially altering equipment to improve performance, such as making bats warmer than they would naturally be due to environmental conditions.

The other options suggest allowances or specific conditions that do not adhere to the rules as they stand. Monitoring the temperature does not negate the fact that using an electric heater is still considered artificial heating. Permitting usage only during specific innings or for warming the field also contradicts the rule regarding artificial means of heating equipment. Thus, the correct answer emphasizes the importance of adhering to the established rules without exception for any artificial mechanisms.