1、drop out

退学;退出(比赛等)

He'd dropped out of high school at the age of 16.

他 16 岁的时候就从中学退学了。

She dropped out after 20 kilometres with stomach trouble.

20 公里后她因胃痛而退出了比赛。

拒绝接受传统规范;离经叛道;摈弃社会习俗

She encourages people to keep their jobs rather than dropping out to live in a commune.

她鼓励人们坚持工作而不是离经叛道地去过公社生活。

2、challenge

挑战;难题

I like a big challenge and they don't come much bigger than this.

我喜欢大的挑战，而所有挑战中再没有比这更大的了。

The new government's first challenge is the economy.

新政府面临的第一个难题是经济问题。

(成功地)应对挑战，迎接挑战

The new Germany must rise to the challenge of its enhanced responsibilities.

一个崭新的德国必须迎接挑战，承担更多的责任。

They rose to the challenge of entertaining 80 schoolchildren for an afternoon.

他们一个下午成功接待了80名学童。

怀疑，质疑(真实性、价值、权威等)

Democratic leaders have challenged the president to sign the bill.

民主党领袖对总统签署这项法案提出了质疑。

The move was immediately challenged by two of the republics.

此项动议立即遭到其中两个共和国的反对。