设f（x）是可导函数，且$\underset{△x\to 0}{\lim }\frac{f\left(x_0-2△x\right)-f\left(x_0\right)}{△x}=\mathrm{2, }$f′（x₀）=（　　）

    Americans like to travel on their yearly holiday. Today, more and more travelers in the United States are spending nights at small houses or inns(客栈) instead of hotels. They get a room with breakfast the next morning.

    Rooms for the night in private(私人的) homes with breakfast have been popular with travelers in Europe for many years. In the past five or ten years, these bed and breakfast places have become popular in the United States. Many of these American's bed-and-breakfast inns are old historic buildings. Some bed-and-breakfast inns have only a few rooms, while others are much larger. Some inns do not provide telephones or televisions in the rooms, but others do.

    Staying at a bed-and-breakfast inn is much different from staying at a hotel. Usually the cost is much less. Staying at an inn is almost like visiting someone's home. The owners are glad to tell about the areas and the interesting places to visit. Many vacationers say that they enjoy the chance to meet local families.

二战后，日本经济持续高速发展，一跃成为仅次于美国的世界第二经济大国。日本成为第二大经济大国是在20世纪（   ）