单项选择题
In order to remove the carbon deposit from the threaded recess, we can use（）
A.a driver B.a scraper C.a tap D.a file
单项选择题 Waste oil should（）
单项选择题 All items such as steam pipes, exhaust pipes and fittings which, because of their location and operating temperature, present a hazard should be adequately lagged.That means the items should（）
单项选择题 In machinery space, the valves, pipes should be（）
