2. To their credit the four countries do work together in some areas (eg, the currency and international relations ), but they still have very different institutions.

句中的do用来强调谓语动词，后面所接的动词原形并不局限于行为动词，还可使用be动词。do的这种用法只用于肯定句中，且do有人称和时态的变化，只用于现在时和过去时两种时态

I do hope you have a merry Christmas.

He did go to the airport yesterday , but he didn't find you.

3. It seemed strange that the man who had developed communism should have lived and died in London.

句中的should 表示意外或惊讶。

It's strange that their team should win the first prize.

should 的其他用法：

1） should 可表示"义务，应该"。用于should do或should have done结构中,其中should have dong意为"本来应该已经...却；要是已经...就好了"

I should been kinder to him.

2） should 用来表示命令、提议、愿望等的that从句中，意为"应该；必须"

She demanded that they should leave at once.

3） should 与疑问词连用，表示意外、惊讶、纳闷等，意为"究竟是；到底"

I don't understand why she should have made such a mistake.

五、语法分析： 过去分词作宾语补足语

在英语中，过去分词可以用作宾语补足语。能用作宾语补足语的过去分词一般都是及物动词，表示被动意义或王城意义，有时候两者兼而有之。作宾语补足语的过去分词与宾语有逻辑上的动宾关系，即宾语是过去分词动作的对象。本文对常见几种用法进行分析：

解释 例子 过去分词用在表示状态的动词keep,leave等的后面 They kept the door locked for a long time.

Don't leave the windows broken like this all the time. Have+宾语+过去分词表示两种含义 1) 表示让某人做某事

I have my bike repaired.

2) 表示遭遇到不幸；受打击

My elder sister had her wallet stolen on a bus last month. 在make+宾语+过去分词这种结构中，过去分词的动词必须表示结果 I raised my voice to make my self heard.

They managed to make themselves understood using very simple English.