where will the 2012 olympic games take place

where will the 2012 olympic games take place
A sure B certain C positive
但是谁可以帮我解释一下.是固定搭配么
真是不好意思
还有一句没写上
It's ( ) that London will hold the games.

先帮你纠正一下大小写：
Where will the 2012 Olympic Games take place
只能选择B--certain.如你所说,这是固定搭配的,也就是英语里所说的idiomatic usage(习惯用法).
另两个词可在以下举行里使用：
I am sure that London will hold the Games.
I am positive that London will hold the Games.
其实,certain也能在这个句型里使用：I am certain that London will hold the Games.
这就叫语感!