Which of the following is a common ignition source during welding and cutting operations?

Sparks are a common ignition source during welding and cutting operations due to the high temperatures and intense energy produced during these processes. When metal is heated, particularly during welding, it can produce sparks that can ignite surrounding flammable materials. The nature of welding and cutting involves molten metal and the potential for flying debris, making it essential to manage sparks to prevent fires or explosions.

In contrast, flammable liquids, while they can certainly act as ignition sources, are not inherent to the welding process itself but rather depend on their presence in the environment. Sand does not ignite and is used to suppress fires rather than create them. Cold metal, on the other hand, does not produce sparks or heat sufficient to serve as an ignition source, rendering it ineffective in this context. Thus, the presence of sparks during welding and cutting operations makes them the primary concern for fire hazards.