Final answer:
Starbucks entered the bakery industry through the method of acquisition by purchasing the established bakery La Boulange, which fits into Starbucks' horizontal integration strategy.
Step-by-step explanation:
When Starbucks purchased the bakery company, La Boulange, it used the method of acquisition to enter into the bakery industry. This is not a joint venture since Starbucks is not entering into an agreement with another party to undertake a particular business project, but rather is purchasing an entire company. It is also not an internal new venture because Starbucks is not starting a new business from scratch within its existing structure.
Lastly, although this move can be part of Starbucks' overall horizontal integration strategy, which refers to acquiring a business operating at the same level of the value chain in a similar or different industry, the specific method used here is an acquisition as they purchased an already established company in bakery operations.