But the professor says it is difficult to find enough feathers from a single dinosaur to recreate all its colors.

VOA: special.2010.03.16

But it's a difficult claim because even as Milton makes this claim, he manages to undermine its force.

但这是困难的，因为即便是弥尔顿做出了这一宣告，他也打算降低它所蕴含的威力。

耶鲁公开课 - 弥尔顿课程节选

And we'll look back maybe and see how that difficult text would've looked in its original context.

我们会倒回去看看这一不同文本,在其原背景下是什么样的。

耶鲁公开课 - 新约课程节选

He says the actively changing nature of the Internet makes it difficult to stay current in studying its effects.

VOA: special.2010.01.28

You can train it to flap its wings to escape a situation but it's very difficult to get it to flap its wings for food.

你可以训练鸽子,通过扇动翅膀来脱离某个情境,但却很难通过训练鸽子扇动翅膀来进食。

耶鲁公开课 - 心理学导论课程节选

Industry leaders, meeting this week in Malaysia, were told that their industry faces its most difficult situation ever.

VOA: special.2009.06.13

The recovery of the Stardust capsule was difficult because of its high reentry speed.

VOA: special.2009.09.30

But the timing of its opening in January has been difficult.

VOA: special.2010.03.31

Crystal says the dynamic nature of the Internet makes it difficult for comprehensive analysis of its effects to stay up-to-date.

VOA: standard.2010.01.16