Question

[英语达人请进] 关于新概念2 Lesson46的问题

Lesson46内容
When a plane from London arrived at Sydney airport,
当一架来自伦敦的飞机抵达悉尼机场时，
workers began to unload a number of wooden boxes which contained clothing.
工人们开始卸下装有服装的一批木箱。
No one could account for the fact that one of the boxes was extremely heavy.
其中有只箱子特别重，可谁也弄不清是怎么回事。
It suddenly occurred to one of the workers to open up the box.
突然一个工人想到打开箱子看看。
He was astonished at what he found.
看到的情景使吃惊，
A man was lying in the box on top of a pile of woollen goods.
箱内有一个人正躺在一堆毛织品之上。
He was so surprised at being discovered that he did not even try to run away.
他由于被人发现而感到非常吃惊，甚至都没有企图逃跑。
After he was arrested, the man admitted hiding in the box before the plane left London.
此人被逮捕后，承认他是在飞机离开伦敦前躲进箱里的。
He had had a long and uncomfortable trip, for he had been confined to the wooden box for over eighteen hours.
他经历了一次漫长而又难受的旅程，因为他在那木箱里闷了18个多小时。
The man was ordered to pay $3,500 for the cost of the trip.
此人被责令交付旅费3,500英镑，
The normal price of a ticket is $2,000!
而正常票价是2,000英镑！

问题：其中的一句“It suddenly occurred to one of the workers to open up the box.
突然一个工人想到打开箱子看看。 ”
书上解释“it”是先行词，主语是动词不定式“to open up the box”
我不太明白。这个事什么句型?动词不定式是怎么回事？

He was so surprised at being discovered that he did not even try to run away.
他由于被人发现而感到非常吃惊，甚至都没有企图逃跑。
这里出现了being，这是什么句型？被动式？这个being和完成时里面的been各怎么用？

Answer 1

这是一个简单句。不定式短语to open up the box 应理解成真主语，形式主语是it. 先行词后面接定语从句，一般由名词，代词担任。
句型so...that ... 表示如此、、、以至于、、、that 引导结果状语从句。
eg. He is so suprised that he couldn't say a word. 他吃惊得一句话也说 不出来了。
being discovered 用做介词at的宾语， 是动词discover 的被动形式，这句话说成The worker was suprised at discovering （the man in the box）意思不变。
been 是助动词， 用来构成被动语态的完成时。