21. 10:35 輔鍋爐燃油切斷由於鍋爐極低水位跳脫裝置作動，翻譯成英文為10:35 Aux. boiler fuel oil cut-out due to ______________ trip device actuated.，其空格為下列何者？ (A) flame eye failure (B) high steam drum pressure (C) low-low water level trip (D) low fuel oil temperature