Vertical integration refers to the integration between the upper and lower reaches of the entire industrial chain. The main purpose is to control certain resources and ensure supply, such as acquiring upstream raw material suppliers or owning certain channels to expand sales. Or similar products, operating similar businesses, and merging between companies that provide the same business, the main purpose is to bring together small-scale enterprises to form an enterprise group to achieve economies of scale. According to the above definition, which of the following is horizontal integrations? ["Lao Zhang built a vegetable and fish farm breeding base to ensure the quality of his hotel's food supplies.", 'Due to the economic downturn and the weak property market, a real estate agent has started to enter the e-commerce field.', 'In order to expand business, a company unites with a university to take the road of combining production, learning and research.', 'A well-known dairy producer acquires 85% of a dairy company.']