I have seen this question created a lot of confusion. Here is a humble explanation.
My question was "'What are included columns in SQL Server 2008?"
There is no difference of included index in SQL Server 2005 and SQL Server 2008. Hence, the question is clear. The answer, whatever it is, applies to both SQL Server 2005 and 2008.
I am not discussing the first answer. The second answer was "This is a new feature of SQL Server 2005". This statement is correct because SQL Server 2005 introduced it and SQL Server 2008 just kept the feature same.
The third answer is the actual definition, hence correct.
This two out of three is correct, hence the check boxes are used.
I have tried to make the flat question a tricky one. I am really sorry if there is still any ambiguity.