1、vulnerable

脆弱的;易受伤害的

Old people are particularly vulnerable members of our society.

老年人是社会中尤为明显的弱势群体。

易感染（某种疾病）的；易患病的

People with high blood pressure are especially vulnerable to diabetes.

有高血压的人尤其易患糖尿病。

Plants that are growing vigorously are less likely to be vulnerable to disease.

生命力强的植物不容易得病。

易受伤害的;易受影响的

Their tanks would be vulnerable to attack from the air.

他们的坦克易受到空袭。

a table showing which cars are most vulnerable to theft.

易被盗车辆一览表

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。