单项选择题 Diesel fuel is relatively safe to handle due to its low volatility, but the fumes will self-ignite and continue to burn steadily if the fuel is heated to the （）.

单项选择题 If the buoyant force on a ships hull is equal to or greater than the displacement tonnage, the ship will （）.

单项选择题 When fighting an electrical fire, you should first （）.