单项选择题
A.drill cooled
B.hole cooled
C.tube cooled
D.bore cooled
单项选择题 Top piston rings are plasma coatedIt gives added safety for the of new lines（）
单项选择题 For auxiliary engines the permissible overload is （） for one hour every twelve hours.
单项选择题 The scavenge air receiver is of a simplified and modular design with integral non-return flaps, hanging cooler and two auxiliary air blowers（）