VOA慢速英语:Study Warns of Dangers to World's Mangrove Forests

keep的用法

1)意为"保存；保留；保持；保守"。如：

Could you keep these letters for me, please? 你能替我保存这些信吗？
I'll keep a seat for you.我给你留个座位。
It can help to keep vegetables, fruit and meat for a long time in hot summer. 在炎热的夏天，它有助于蔬菜、水果和肉类长时间保鲜。
Can you keep a secret? 你能保守秘密吗？

2)意为"照顾；养活"等。如：
She kept her sister for a week while her sister was ill.她妹妹有病时，她照看她了一个星期。
I have a family to keep.我得养活一家人。

3)意为"留下；不必还"。如：
You can keep the pen if you like it.你要是喜欢就把钢笔留下吧。
Keep the change.不用找零钱了。

4)意为"遵守；维护"。如：
Everyone must keep the rules. 人人必须遵守规章制度。
The teacher is keeping order in class.老师正在课堂上维持秩序。
 
5)意为"售；卖"。如：
The shop keeps everything you need.那家商店里出售的东西应有尽有。
He keeps everything you will drink.他出售你想喝的各种饮料。

6)意为"记(日记、帐等)"。如：
She keeps a diary every day.她坚持每天记日记。
He keeps exact accounts of the money he spends and a diary of the events of his holidays.他详细地记载他所花的钱数和假期中所发生的事情。

7)意为"使……保持某种(状态、位置或动作等)"。这时要在keep的宾语后接补足语，构成复合宾语。其中宾语补足语通常由形容词、副词、介词短语、现在分词和过去分词等充当。如：
We should keep our classroom clean and tidy.(形容词)我们应保持教室整洁干净。

2.The study says mangrove trees provide more than one and a half billion dollars worth of services to ecological systems worldwide.

one and a half带分数

带分数也是常见的英语数词表达。所谓带分数，实际上是“整数＋分数”，表达时分而述之，只是整数部分与分数部分要用连词 and连接。当带分数修饰名词时，该名词通常是复数，但若名词置于整数one或a之后，则用单数。“带分数＋名词”作主语时，谓语动词根据临近原则要用复数。例如：

　　You should finish the work within one and a fourth hours．
    你应在1.25小时内完成工作。

　　The atom breaks up in a minute and a quarter．
    原子在1.25分钟内裂变。

3.And they serve as nurseries for shrimp and other saltwater organisms.

serve as担任,充当,起…作用,被用作

The general had served as a soldier in the earlier war.
在早期的战争中, 这位将军曾当过士兵。

We found that birch bark could serve as paper.
我们发现桦树皮可以作纸用。

4.Beth Polidoro says they may disappear within the next ten years unless action is taken to protect them.

unless是连词,意为“如果不”、“除非”。例如:
　　One can’t learn a foreign language unless he studies hard. 不下苦功夫是学不好外语的。
　　I will not go unless I hear from him.
　　如果我不收到他的来信,我就不去。
　　[特别提醒] unless连接一个条件从句,等于if…not, 不同点在于:if …not是口语, unless为书面语,unless有否定意思。例如:
　　I shall go there unless it rains.
　　= I shall go there if it doesn’t rain.
　　我去,除非下雨(如果不下雨,我就去)。