单项选择题 The piston crown employs the usual jet-shaker principle with an arrangement of cooling bores in the crown so that the surface temperatures of the crown are moderate with a very even distribution（）

单项选择题 The development goals for a large marine engine are many often interact and in some cases even with each other（）

单项选择题 The key feature of the Sulzer RT-flex system is that it gives complete freedom in the and operation of fuel injection and exhaust valve actuation（）