Economics is the study of how societies use scarce resources to produce valuable goods and services and distribute them among different individuals. If we think about the definitions， we find two key ideas that run through all of economics:
经济学特别是宏观经济学中说的投资是耐用资本品如厂房设备的生产，而平常说的“投资”是指购买资产如股票，这和经济学中的投资不同，为了区分，这种投资被称为金融投资。
说再见就是死去一点点。
过去从未死去，它甚至还没有过去。
Sustainability isn't an option—it's our responsibility to future generations.