Inflation occurs when: （ ） A: the stock of goods and services increases and the quantity of money in circulation decreases. B: the money supply decreases and the output increases. C: output increases faster than the money supply. D: the quantity of money in circulation rises faster than the stock of goods and services.

The marginal cost often increases asproduction increases up to a point because of efficiencies created by largeramounts.

以下各句正确的是__________。 A: An increase in demand is likely to cause a rise in prices. B: Increases in demand usually lead price increases. C: If demand increases; as a result, prices tend to rise. D: Increases in price are often resulted by increases in demand.

Research has to focus on the cost benefit of factors such as reliability because ______. A: as reliability increases, manufacturing final cost may increase B: as reliability increases, manufacturing costs and the final cost will decrease C: as reliability decreases, manufacturing costs and the final cost will decrease D: as reliability increases, manufacturing costs and the final cost may increase

When a factory is operating in the short run, A: it cannot alter variable costs. B: total cost and variable cost are usually the same. C: average fixed cost rises as output increases. D: it cannot adjust the quantity of fixed inputs.