Indeed, the purple colour extracted from a snail was once so costly that in society at the time only the rich could afford it.

的确，从蜗牛身上提取的紫色物质曾经非常昂贵，在当时的社会，只有富人才能买得起。

youdao

They can only land once—the time when they die.

它们只能落地一次——那就是死亡的时候。

youdao

We internally activate many thoughts at once, but we can retrieve only one at a time.

我们能一次激活许多不同的想法，但只能集中注意力思索其中的一个。

youdao

Once each time. Right? I only do one swap potentially, it-- though not one potentially, each time at the end of the loop I do a swap.

每次循环做一次，对么？我其实,就可能做了一次交换，也许并不是可能，每次循环的结束我都得做一次交换。

麻省理工公开课 - 计算机科学及编程导论课程节选

Now we can afford a fairy-tale getaway that we'd only dreamed of once upon a time.

BBC: Daily deal: Vermont fairy-tale

Placing a big one-time bet "cuts the house edge to its bare minimum because it works on your stake only once, " says Anthony Curtis, a one-time professional gambler and president of lasvegasadvisor.com.

FORBES: Magazine Article

So, my own plan for Silicon Dragon events is to not only to hit the Valley but also tap Tsinghua once spring-time arrives.

FORBES: Hanging out with VCs at Tsinghua