网友对这两个句子的结构理解有误，重新分析如下：

第一个例句：It was found that her blood contained poison.

她的血液中发现有毒液。

这是一个被动句，主动语态是：People found that her blood contained poison.

第二个例句：She finds it a strain to meet new people.

她和生人见面总会局促不安。

这是 “find + 宾语 + 宾补” 结构。有时，find 的宾语是不定式或从句，太长须后置，原位置用it 替代。现分别举例：

一、不定式作真实宾语：

We found it quite pleasant to work with him. 

我们发现跟他一块工作很愉快。

I felt it hard to communicate with them. 

我感觉难以跟他们交流。

Do you find it funny to see someone sliding on a banana skin? 看见有人踩在香蕉皮上滑倒，你觉得有趣吗？

I find it difficult to do the job well. 

我发现做好这件事不容易。

I find it easy to get on with her. 

我发现她很容易相处。

二、that 从句作真实宾语：

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。

I found it strange that she had not come yet. 

她竟然没来，我发现奇怪。

You may find it astonishing that Charlie was taught to sing as soon as he could speak and dance as soon as he could walk. 

你可能会感到惊奇，在查理刚能说话时大人就教他唱歌，他刚能走路时大人就教他跳舞。

第一个例句：It was found that her blood contained poison.

她的血液中发现有毒液。

结构为 find it that＋从句.

第二个例句：She finds it a strain to meet new people.她和生人见面总会局促不安。结构为find it sb/sth to do.

问题(1)解答如下：

contaminate vt.污染;弄脏,把…弄脏,

contaminate 为及物动词，A contaminate B, A把B弄脏，A把B给污染了。或者A be contaminated by B “A被B给污染了/弄脏了”

It was found that her blood contained poison.

that主语从句，结构有问题，可以说把他的血液把毒物/毒药/毒素污染了吗? 很显然这样是不符合语言逻辑的，因此可以改为下面句子。

(1)It was found that her blood was contaminated by poison.（正确）

(2)It was found that poison contaminated her blood.（正确）

备注：以上不可以用真正that从句放在句首作主语。

(1)That her blood was contaminated by poison was found.（错误）

(2)That poison contaminated her blood was found.（错误）

问题(2)解答如下：

She finds it a strain to meet new people.

她和生人见面总会局促不安。find+形式宾语+宾补+真正宾语

(1)she为句子主语（女她主格代词充当）

(2)finds为句子谓语动词（动词三人称单数充当）

(3)it为形式宾语（它主格代词充当）

(4)a strain为宾补（名词充当）

(5)to meet new people为真正宾语（动词不定式充当）

结构为find it sb/sth to do.

以上句子结构属于6123结构

(1)6表示有6个这样及物动词:find, think, consider, feel, believe

(2)1表示1个形式宾语:it

(3)2表示2种形式宾补:(1)名词(n.);(2)形容词(adj.)

(4)3表示3个不同形式真正宾语：(1)doing; (2)to do;(3)that从句