VOA慢速英语:NASA Working Toward Mission to Mars

1. sustainable adj.可持续的;可以忍受的
例句：Investors yesterday questioned whether the gains in membership were sustainable.
投资者昨日对会员人数增长的可持续性提出了质疑。

2. stimulate vt.刺激;激励，鼓舞
例句：A sketch can stimulate one's own imagination.
图形能促进一个人的想象力。

3. require vt.要求;需要
例句：All big decisions require a balance of soft and hard information.
所有重大决策都需要软信息与硬信息的平衡。

4. announce vt. 宣布;述说
例句：Please announce to the children that there will be no school this afternoon.
请通知孩子们今天下午不上课。

5. encourage vt.鼓励，鼓舞
例句：As to writing, we do not encourage them to scrawl too early.
至于书法，我们不鼓励他们过早地乱写。