Monopoly: On the basis of the highly developed concentration of production and profitable capital, a one-person enterprise or a few large enterprises has the sole, exclusive, or joint control of the production and sales of products in the corresponding sector. Which of the following is a monopoly:. ['A catering chain company implements unified national pricing in both economically developed and backward areas.', 'In order to curb the decline in the price of a certain home appliance, several major manufacturers have agreed to jointly maintain an agreed price.', ' multinational company sells a certain model of products worldwide through its factories in China.', 'In order to curb excess industries, the government strictly limits the establishment of new factories in related industries.']