Final answer:
General Motors' purchase of tires for their automobiles is classified as Operating expenditure, which is normal for the routine functions of manufacturing their products.
Step-by-step explanation:
When General Motors purchases tires for their automobiles, this expenditure can be classified as b. Operating expenditure. This is because operating expenses are costs associated with running the day-to-day operations of a business. In this case, as General Motors is in the business of manufacturing automobiles, tires are a necessary and routine purchase for the completions of its products and are thus considered operating expenses rather than capital expenditures, which typically refer to long-term investments in the company, such as purchasing machinery or building a new plant.