McDonalds use all 3 sectors, however, they are primary located in the tertiary sector, the reason why they technically use all 3 sectors, is that they need the potatoes and the meat from the primary sector, then the secondary sector will peel the potatoes and shape the meat, send them off to McDonalds where they cook and sell it on for a large profit, in McDonalds, all 3 sectors must work together to allow McDonalds to function the their full potential, as without stock, there is no business.

The farmers grower the potatoes, and breed the animals for meat