Concat itself is a an extension method implemented as such.

代码中的Concat是一个扩展方法(extension method)，其实现如下。

youdao

JUnit 4 is a radical new framework, not a an upgraded version of the old framework.

JUnit 4基本上是一个新框架，而不是旧框架的升级版本。

youdao

Education (at least high school) is a an essential foundation for every single person today.

今天教育(至少高中教育)对于每个人是十分重要的基础。

youdao

closing an air field in a populated area and building a new one on an existing U.S.base in the northern part of the island.

VOA: standard.2009.10.20

If you put Beta and you're paired with Alpha, you'll get a C and your pair an A.

如果你选β你对手选α,你得C你对手得A

耶鲁公开课 - 博弈论课程节选

Because I feel like a portrait is an answer to a question which is, 'What was this person like?'

因为我觉得肖像画是这样一个问题的答案，那就是“这个人长什么样？"

关于现代美术 - SpeakingMax英语口语达人

So Bank B paid Bank A an upfront premium for what is effectively an insurance policy.

FORBES: Greek Election: Does It Matter?

He said there were some rare finds including a an early docu-drama on a Zeppelin raid on London.

BBC: Lost radio shows back on air

"It's the difference between an A and an A-plus, " he was quoted as saying by AP news agency.

BBC: Hubble gyros fixed after struggle