It was once used to keep food in Europe.

在欧洲，它曾被用来保存食物。

youdao

Believe it or not, yellow was once used to mean stop.

信不信由你，黄色曾经用于表示停止。

youdao

White dwarfs are stars that have burned up all of the hydrogen they once used as nuclear fuel.

而白矮星则是将其曾用作核燃料的所有氢原子都燃烧殆尽的恒星。

youdao

Such as washing of hands, coughing into sleeve and throwing away tissues once used.

VOA: standard.2010.04.29

I once counted the number of times he used the word the letter--O--in that poem, and I quit counting.

我曾经数过他到底在诗里用了多少个"啊",最后我放弃了

耶鲁公开课 - 美国内战与重建课程节选

n l m s Once we have chosen a certain mix of n, l, m and s, it is used once for that particular atom.

一旦我们选定了一组量子数，它就只能被一个固定原子所有。

麻省理工公开课 - 固态化学导论课程节选

They now bring groups through the desert, often along trails once used by Pancho Villa's army.

ECONOMIST: Illegal immigration

Nextel began as a crazy quilt of local radio networks once used for taxi dispatch services and the like.

FORBES: "We're On A Collision Course"

One example of the problem: U.S. soldiers once used bits from ancient Babylon to fill sand bags.

NPR: U.S. Military Deals Cards to Save War-Torn Sites