单项选择题 A lube oil sample taken from the main engine lube oil system has dark yellow opaque color.This is the result of （）

单项选择题 When you are transferring fuel oil to the setting tanks, precautions to be observed should include （）

单项选择题 Heavy fuel oils generally have an upper average ash content of 0~1% by weight.Which of the following conditions could be expected if the ash content increase above this amount?（）