1. You have all heard It repeated that...
it 是形式宾语，that 从句是真正宾语，也就是宾语从句。形式宾语和真正宾语，这个叫法就不是同位语了。有的语法书称为同位语，是不合理的称呼。这样的表达很常见：
We thought it necessary that the two sides should stop arguing. 我们认为，双方停止争论是必要的。
He considered it a good thing that the parliaments would be involved. 他认为，议会将卷入其中是好事一桩。
Ann felt it an justice that she had been automatically blamed. 安觉得，她已自动接受职责是公正的。
They find it a mystery that he has never mentioned his parents. 他从来没提到过自己的父母，他们发觉真是个谜团。
We consider it necessary that the machine should be oiled regularly. 我们认为，有必要对这台机器经常加油润滑。
Under the circumstances I feel it right that you should know. 在这种情况下，我觉得你应该知道。
I found it strange that she had not come yet. 她竟然没来，我发现奇怪。
Mr. Black made it clear that the students should prepare every lesson. 布莱克先生明确指出，学生应准备每一节课。
I think it important that we should keep calm. 我认为我们保持冷静是很重要的。
I consider it best that you should stay here. 我认为你最好住这儿。
They haven’t made it known where they are to hold the conference. 他们还没宣布会议在哪里开。

2. I take it that they will succeed sooner or later.
take 是个多义词，其中有一个意思是：“认为”。但是，这个词不像 think 那样，直接跟that从句，它一般只接名词或代词作宾语。不可直接说：I take they will succeed sooner or later. 这时，需要加一个形式宾语it，然后再跟 tha t从句。
I take it that you have been out.  我猜你刚出去回来。
I take it that you are leaving tomorrow. 我以为你明天走。
Can I take it that our policy has your support ?  能否认为我们的政策得到您的支持?
May I take it that you will sign the document?  我相信你会在文件上签字的吧?
Are we to take it that you refuse to co-operate?  我们是否可以认为你拒绝合作？
Can I take it that we are all satisfied with the plan ? 我可以认为我们对这个计划都满意了吗?
We take it that you will act according to the final agreement. 我们认为你方是会按照最后协议行事的。
You may take it that we shall not be asking you to rejoin the union. 你可以认为我们将不会要求你重新加入工会。
When I didn't hear from her, I took it that she was on holiday. 我没收到她的信时，我以为她在度假。

我觉得 同位语就是解释前面的n 通常这个n是抽象的 并且通常同从that是不作成分的 和定从相区分