What causes the formation of white smoke?

The formation of white smoke is primarily associated with excessive air entering the combustion chamber in an engine. When there is an overabundance of air relative to the fuel, the combustion process is less efficient, leading to incomplete combustion. This results in the production of tiny water droplets or small particulate matter, which give the smoke its white appearance. It is indicative of an air-fuel mixture that is not properly balanced, suggesting that the combustion is occurring at a level that does not achieve optimal burning of the fuel.

In contrast, insufficient fuel would likely cause a lean mixture, which could produce blue smoke or result in no smoke at all. High temperatures could lead to complete combustion, producing only water vapor. Low pressure, depending on the context, doesn't directly correlate with the formation of white smoke in the same manner that excess air does. Thus, the presence of too much air is the clear reason for the white smoke observed in this scenario.