单项选择题
The injector pump is operated by a cam which drives the plunger （）.
A.top and bottom B.to and fro C.up and down D.back and forth
单项选择题 The injector pump is operated by a cam which drives the （） up and down.
单项选择题 The injector pump is operated by a cam which drives （） up and down.
单项选择题 The indications of a scavenge fire are excessive black smoke, （） and peeling from scavenge trunking.
