Final answer:
Excessive spatter in the nozzle during welding is most closely associated with causing 'c. Loss of shield and porosity,' which can lead to weakened welds.
Step-by-step explanation:
The question relates to the welding process, specifically the issues that can arise from excessive spatter in the nozzle during welding. Excessive spatter can have several negative effects on welding quality, but of the options listed, it is most closely associated with causing c. Loss of shield and porosity. Spatter is the spray of molten material that can be produced by the welding arc, and when it builds up in the nozzle, it can obstruct the gas flow which is necessary to protect the molten weld pool from atmospheric contamination. This interference with the shield gas can lead to porosity in the weld, which is the presence of small cavities or holes caused by trapped gases. Porosity can significantly reduce the strength and integrity of a weld.