You administer a Microsoft SQL Server 2012 database that contains a table named OrderDetail. You discover that the NCI_OrderDetail_CustomerID non-clustered
index is fragmented. You need to reduce fragmentation.
You need to achieve this goal without taking the index offline. Which Transact-SQL batch should you use?

A.
CREATE INDEX NCI_OrderDetail_CustomerID ON OrderDetail.CustomerID WITH DROP EXISTING

B.
ALTER INDEX NCI_OrderDetail_CustomerID ON OrderDetail.CustomerID REORGANIZE

C.
ALTER INDEX ALL ON OrderDetail REBUILD

D.
ALTER INDEX NCI_OrderDetail_CustomerID ON OrderDetail.CustomerID REBUILD

Explanation:
http://msdn.microsoft.com/en-us/library/ms188388.aspx