of是介词，一般后接名词，代词或动名词。for同样是介词，后接名词，代词或动名词。意义多为“为了”。
1、Would you say what you felt was a feeling of betrayal?
你是否觉得有一种被人出卖的感觉？
2、A flock of birds flew towards us slowly from far away.
一群鸟儿从远处朝我们缓缓飞来。
3、We could all do with a cup of tea .
要是能给我们都来杯茶就好了。
4、Isn't that enough for you?
那对你来说不够吗？
5、I knew he worked for a security firm.
我知道他在一家保安公司工作。
6、She appears nightly on the television news, speaking for the State Department.
她作为国务院的发言人，每晚都会出现在电视新闻中。