单项选择题
The rotating range of the low speed diesel engine is usually lower than （）.
A.100 rpm B.200 rpm C.300 rpm D.500 rpm
单项选择题 Before using or operating any equipment, you should first （） its manual thoroughly and understand its contents（）.
单项选择题 When we say that two objects have relative motion, we mean （）.
单项选择题 The trouble-free life of an engine indicates （）.
