1．Polly found herself staring up at a man standing with his hand resting on her arms. 波莉发现自己身边站着一个男人，他的手搭在她的胳膊上。她睁大了眼睛盯着他看。
1）句中staring up at a man standing with his hand resting on her arms充当宾语补足语，其中standing with his hand resting on her arms作定语，修饰a man。
2）find oneself… 发现自己处于某种状态，不知不觉……, 后面可接多种成分作宾语补足语。例如：
He found himself walking in the direction of the bus station.  他不知不觉朝汽车站的方向走过去。
When she came to herself, she found herself in hospital. 醒来时，她发现自己在医院里面。
I found myself surrounded by a group of children. 我突然发现一群孩子围着我。

2．The face that she saw was that of an old man. 她看到的是一张老年男子的脸。
句中第一个that是关系代词，引导定语从句，并在从句中作宾语；第二个that是代词，代指前文提到的the face。that用来代替上文中出现的名词，表示与前面同类的东西，既可指代可数名词，也可指代不可数名词，常要求有后置定语，一般不指人。
The price of meat is higher than that of fish.   肉的价格比鱼的价格高。
The population of China is much larger than that of Japan.  中国的人口比日本的人口多多了。

3. The chances of being attacked by a shark are very small compared to other dangers.与其它危险相比，受到鲨鱼攻击的可能性是很小的。
compare…with… 表示“把……和……相比较”，侧重指两者间的区别；compare… to…意思是“把……比作……”，着重注意两者之间的相似点; 而compared to和 compared with二者都用作状语，意义基本相同，可互换。  
Compare this car with that one, and you will find the differences between them.
把这辆汽车和那辆汽车进行比较，你就会发现它们之间的区别。
The shape of Italy on the map is often compared to a long boot.
地图上意大利的形状常被比喻成一只长靴。 
Compared to/ with other women, she is much luckier.
和其他妇女相比，她幸运得多了。

4. The low number of attacks that happen every year proves that sharks do not feed on humans if they have the choice.  鲨鱼攻击人类的事件每年并不多见，这就证明，如果有机会选择，鲨鱼并不以人为食。
这是一个复合句，其中第一个that 是关系代词，引导一个定语从句，修饰attacks；第二个 that是连接词，引导一个宾语从句；if从属连词引导条件状语从句。feed on“以……为食，吃，以……为能源”。例如：
As is well known, cattle feed on grass.
众所周知，牛以草为主食。
The gas turbine feeds on the fuel it pumps.
这台燃气轮机以它抽入的燃料为能源。