Opposition Republicans responded to the latest figures by focusing on specific sectors that continue to lag and renewing their assertions that steps President Obama has taken since he came to office, such as the $787 billion stimulus, have had little impact on the economy.

VOA: standard.2009.12.05

These are things that must be taken in from the environment because your body cannot manufacture them and they promote specific chemical reactions in the body.

这些都是必须从外界摄取的物质,因为无法通过自身合成,它们能促进体内特定的化学反应

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

These are things that must be taken in from the environment because your body cannot manufacture them and they promote specific chemical reactions in the body.

这些都是必须从外界摄取的物质,因为无法通过自身合成,它们能促进体内特定的化学反应

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选