单项选择题 Modern centrifuge designs enable continuous over a considerable period of timeThis is achieved by which is timed to discharge the sludge at regular intervals（）

单项选择题 The oil sump, a light welded design, is mounted on the engine block from below and sealed by （）

单项选择题 The air required for combustion is taken from the engine room through a filter fitted on the turbochargerThis reduces the risk for too and contamination of the combustion air（）