VOA慢速英语:A Possible Safe New Way to Kill Mosquitoes That Spread Malaria

1.Israeli researchers say they have developed a substance that attracts and kills mosquitoes infected with the malaria parasite.

that attracts是定语从句，修饰substance。infected with是过去分词做后置定语，修饰mosquitoes。

2.But the area is full of little ponds in there, so it is impossible to stop mosquitoes from flying from an untreated pond to a treated pond.

be full of充满

例句：be full of wrinkles
      布满皱纹

3.Boric acid has been used to kill other insects including cockroaches, termites and ants inside homes since the middle of last century.

现在完成时

现在完成时的时间状语有now, today, tonight, this week, this year, already, yet, just, recently 等；过去完成时的时间状语有by…,

at..., before…等。当时间状语表示一段时间时，现在完成时和过去完成时都可以用for或since 引导的状语。

Have you had your lunch yet? 你吃午饭了吗？

They had done the work at five o'clock. 五点钟的时候他们已经完成了那项工作。

现在完成时和一般过去时谈的都是已发生的事，区别就在于现在完成时表示的动作与现在有关系，或是对现在有影响；而一般过去时单纯谈过去的事情，与现在没有关联。一般情况下，只要有明确的过去时间状语，就可用一般过去时

She has written some short stories. 她写了一些短篇小说。

She wrote some short stories yesterday. 她昨天写了一些短篇小说。

I've learnt a lot from you, so thank you very much.

我向你学到了很多东西，因此很感谢你。

I learnt a lot there. 我在那里学到很多东西。

现在完成时的基本构成是have/has +过去分词，而一般过去时的谓语动词用过去式

I have seen that film. 我看过那部电影了。

I saw that film last night. 我昨天晚上看了那部电影。

现在完成时常与just, already, ever, never等副词和these days, this week, since…, for…等表示一段时间的时间状语连用，而一般过去时通常与表示过去的时间状语连用，如yesterday, last week, two years ago, just now等

I haven't seen him these days. 我这些天没见到他。

I didn't see him yesterday. 我昨天没见到他。