单项选择题
A.the trunking should be opened up
B.should the trunking be opened up
C.the trunking should not be opened up
D.should the trunking not be opened up
单项选择题 On top of scavenging air box is mounted a strong cast iron frame for each cylinder known as（）
单项选择题 On the top of the cylinder is mounted the cylinder cover which is pressed onto （） of the cylinder liner by means of nuts and studs.
单项选择题 On opposite ends of a single shaft of a turboblower are a gas driven （）and a air compressor, which are sealed each other.