单项选择题
Diesel engines are considered safer than gasoline engines because（）.
A.they are more heavily built B.the fuel used is less volatile C.they can be easily reversed D.they operate at a lower speed
单项选择题 Before starting any diesel or gasoline engine，which of the following must be checked? （）
单项选择题 All marine low-speed diesels are of what design?（）
单项选择题 All diesel engines are classified as（）.
