When is it safe to remove the radiator cap?

The correct choice is to only remove the radiator cap when the engine is cooled. This is essential for safety reasons. When the engine is hot, the coolant inside the radiator is under pressure and can reach high temperatures. Removing the radiator cap while the engine is hot can lead to a sudden release of steam and boiling coolant, which can cause severe burns or injuries.

By ensuring that the engine is cooled down before removing the radiator cap, you minimize the risk of such dangerous situations. Always allowing the engine to cool before handling any components of the cooling system is a best practice in vehicle maintenance to protect both yourself and the vehicle's parts.