Final answer:
Delphi Automotive would be most concerned with losing market share if General Motors starts manufacturing their own automotive parts, as this could lead to reduced sales for Delphi.
Step-by-step explanation:
When General Motors considers making its own automotive parts, Delphi Automotive Supply Company, which supplies parts to GM, would primarily be concerned with the potential for losing market share. If GM begins to manufacture their own components, Delphi may face reduced orders, leading to lower sales. In a world where automobile producers like Toyota, Honda, and Volkswagen provide stiff competition, it's essential for suppliers like Delphi to maintain their business with major manufacturers like GM to sustain their position in the industry. Delphi's focus would likely be on the aspects of business that could be directly impacted by GM's decision, which in this case is the market share occupied by Delphi.