[判断]A firm will shut down in the short run if revenue is not sufficient to cover its variable costs of production.
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[判断]A firm operating in a perfectly competitive market earns zero economic profit in the long run but remains in business because the firm’s revenues cover the business owners’ opportunity costs.
A. 对
B. 错
下列各项属于股票投资优点的有（ ）。
A. 能降低购买力的损失
B. 流动性很强
C. 投资风险低
D. 收入稳定性强
证券就用以证明或设定权利所做成的书面凭证。（ ）
A. 对
B. 错
证券投资具体分为项目投资和金融投资。（ ）
A. 对
B. 错
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