Thanks for the question.

Almost got it wrong when I read this from SQL Authority, Pinal Dave: "They can be used on Views only if they are persisted views."

- http://blog.sqlauthority.com/2008/09/01/sql-server-2008-introduction-to-filtered-index-improve-performance-with-filtered-index/

So I was wondering if there were 4 correct answers until I read in BOL, "You cannot create a filtered index on a view."

- http://technet.microsoft.com/en-us/library/cc280372.aspx