Which condition could lead to an unstable fuel supply affecting the burner?

An unstable fuel supply affecting the burner is primarily caused by a blocked fuel line. When the fuel line is obstructed, it prevents the proper flow of fuel to the burner, which can lead to insufficient fuel availability for combustion. This can result in inconsistent burner operation, leading to inefficient heating, disturbances in flame stability, and potentially hazardous situations such as incomplete combustion or flame fluctuations.

In contrast, consistent environmental conditions, regular maintenance, and proper storage of fuel all contribute positively to the stable operation of the burner. Consistent environmental conditions help maintain optimal operating temperatures, while regular maintenance ensures that any wear and tear or potential issues are addressed before they affect performance. Proper fuel storage helps to maintain the quality of the fuel, preventing contamination and degradation that could otherwise disrupt the fuel supply. Therefore, a blocked fuel line is the only option that directly leads to an unstable fuel supply.