And he is praising four committees in Congress for agreeing on what he calls "a difficult and complex challenge."

VOA: standard.2009.08.08

- Part of the challenge is speed, too, how quickly you can get these answers in terms of getting them in on time.

部分困难也会来自于速度，你多快能做出答案,能否在规定的时间做完。

麻省理工公开课 - 化学原理课程节选

The challenge will be to get legislation on the table that will back up those numbers.

面临的挑战将是进行支持这一目标的立法。

对全球变暖的政策 - SpeakingMax英语口语达人

I am not going to walk away from the American people. I am not going to walk away on this challenge.

VOA: standard.2010.02.06

And scientists have been working on this for years and there's been progress, but it's still a very difficult challenge.

科学家们对此已经研究很久了,并取得了进展,但仍有很大挑战

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

He says fighting traffic congestion, he adds,is an on-going challenge because this urban area continues to attract more jobs and more people.

VOA: standard.2010.07.26

So the challenge thing comes back to the instruction of designer: what are you for on this access?

这样，教育设计者,又重新面临着挑战：,你会支持这项技术吗？

麻省理工公开课 - 媒体、教育、市场课程节选

Another problem is access. Connecting informal communities to the city's water pipeline is a challenge because many are living on the land illegally.

VOA: standard.2010.08.04

And the challenge for scheduling is to pick the things that you want the president to be working on and the president wants to be focusing on proactively rather than just reacting to whatever the crisis on the day was.

安排日程的难处在于,选择事情,选择你要让总统去做,选择总统需要积极投入,而不仅仅是消极回应的,每天发生的大事情。

普林斯顿公开课 - 国际座谈会课程节选

"So I can challenge somebody and they can challenge me just on an on-going basis.

VOA: standard.2010.07.16

Then, the next challenge was to figure out how to keep the dots on the streets because they were going all over the place.

接下来的挑战是,想办法让这些点固定在,街上，因为,它们总是不停地移动。

斯坦福公开课 - Twitter之父Jack.Dorsey演讲：好奇和灵感的力量课程节选

Republicans have taken aim at that, as they continue to attack Mr.Obama on several fronts and challenge the White House over deficit spending and rising debt.

VOA: standard.2010.07.19

It can be challenged on normal... Yeah, open to challenge. -Right.

一般情况下人们可以挑战。,对，人们可以挑战其中的观点，-是的。

普林斯顿公开课 - 人性课程节选

As President Obama loses ground in the debate on overhauling health care, he is using his weekly Internet address to challenge what he calls "phony claims" by his critics.

VOA: standard.2009.08.22

And last June,says Sittenfeld, the House passed the American Clean Energy and Security Act, the first bill out of either chamber of Congress to directly take on the challenge of global warming.

VOA: standard.2010.02.25

On the second day of her Moscow visit, at the end of a European tour, U.S.Secretary of State Hillary Clinton voiced concern at recent attacks on activists and reporters willing to challenge the Kremlin.

VOA: standard.2009.10.14

For Garson,it has been a challenge to put aside his concerns about Haiti, and focus on football and the most important game of his career, but he has a simple message to Haitians.

VOA: standard.2010.02.04