She gave a free concert in the open air, near the Lincoln memorial.

VOA: special.2009.01.25

We, in fact, borrow oxygen or steal oxygen from the air free of charge.

我们事实上免费从空气中,借或者偷氧气。

麻省理工公开课 - 固态化学导论课程节选

He did it to bring more light, he did it to bring more air, he did it to free the flow for capital, money; that's why the department stores are on the boulevards.

他这么做是为了多点光,多点新鲜空气,他为了使资产的流动更为自由,这就是为什么百货商店都建在大道旁边

耶鲁公开课 - 1871年后的法国课程节选