be/live under the impression that
原以为，误以为……
（含义特别强调后来知道这个想法是错的）
请看经典例句：
Though the crew were at fist under the impression that the lost dad been found, the contents of the sea-chest proved them wrong.（新概念英语3.L32）
船员们开始误认为沉船找着了，但海底沉箱内的物品证明他们弄错了。
一、句子结构分析：（让步状语从句）Though the crew were at first under the impression/（同位语从句） that the lost ship had been found, /（主句）the contents of the chest proved them wrong.
I was under the impression that the work had already been completed.
我还以为已经完工了呢。《牛津高阶英汉双解词典》
He's still labouring under the impression that he's written a great book.
他仍然有这样的错觉，以为自己撰写了一部巨著。
He had apparently been under the impression that a military coup was in progress.
他显然以为一场军事政变正在酝酿中。《柯林斯高阶英汉双解学习词典》
Maybe you’re under the impression it takes years of disciplined practice to start to see results.
也许你有一种(错误)印象，那就是要经过多年的严格训练才能看到结果。
Millions of children are under the impression that all a doorman has to do is blow his whistle and a taxi will be there.
成千上万的孩子就有了这样一种(错误)印象：门卫只要吹声口哨，马上就会有辆出租车开过来。
I was under the impression that you couldn't get a parking ticket on private property.
我原以为，你不会在私人物业上拿到停车罚单。
I’m sorry, I was under the impression that you were the manager.
不好意思，我把你错当经理了。
She must be under the impression it was him.
她一定错以为那就是他。
I was under the impression that we shared certain things equally.
我的印象是，我们平等地分享某些东西。
Both Halle and Sethe were under the impression that they were hidden.
哈莉和塞丝都误以为自己被隐藏了。
They were under the impression that all strike offenses had to be violent or serious.
他们原以为，所有罢工行为都必须是暴力或危险的。
She seemed to be under the impression more guests were coming, but nobody else ever came.
她似乎误以为有更多的客人来了，但从来没有其他人来过。
二、the crew后接were,为什么不是was?
当crew指统一的集合体时，其谓语动词用用单数；当它指其分散行动的成员时，其谓语动词用复数：
The train crew runs a railroad train.
列车乘务人员管理列车。
The ship's crew was sluicing down the deck.
船员们正在冲洗甲板。
Crews are working to plug a major oil leak.
船员正在封堵一个漏油的大洞。
The crew are of different nationalities and have no common language.
船员来自不同国家，语言不通。
Ambulance crews were tending to the injured.
救护车上的救护人员在照料受伤者。
The crew are paid to do all the work on the ship.
船员们被雇来做船上所有的工作。
Rescue crews have been digging people out of collapsed buildings.
救援人员一直在倒塌的建筑物废墟中挖掘救人。
上面新概念英语中的例句显然是指一个个的船员个体们，所以用复数。
具有类似用法的名词还有：audience, public, crowd(人群), government, family, class, company, staff, group, college, team, university, committee等。
