（10日照3）下列物质中存在氧分子的是

A．水

B．双氧水

C．二氧化碳

D．液态氧

Marginal benefit is most accurately described as the:（）

A. benefit from producing one more unit of a good or service.

B. benefit an individual gets from consuming an additional unit of a good or service.

C. benefit that must be forgone in order to consume an additional unit of a good or service.