Extention method

http://www.developer.com/net/csharp/article.php/3592216
Following are the interview questions
1.Difference between asp.net 3.5 and 4.0
2.why we are using Ajax.
3.what is Extention method.
4.how the procedure will faster.
5.how to improve the performance of the SQL Server.
6.What is pivot table.
7.did you know generic.