单项选择题 Factor influencing the position of the interface between the liquid seal and the oil in a purifier is （）.

单项选择题 Expansion tank should be used to remove （） from cooling water.

单项选择题 Exhaust temperature increases in all cylinders, the possible cause may be（） (1) increased scavenging air temperature (2) air in fuel pumps and fuel valves (3) fouling of air and gas passages