单项选择题 Oil pressure in the lubrication system is （） the static sea water head to ensure that sea water （） the stem-tube.

单项选择题 Oil is supplied to the cylinder wall and （） by means of mechanical lubricators.

单项选择题 No specific period is given for the renewal of the lubricating oil filter element as this should be done（） a figure of 0√7 bars is shown on the gauge.