Which Transact-SQL command should you use?

You administer a Windows 2008 server hosting an instance of Microsoft SQL Server 2012 Standard
Edition. The server hosts a database named Orders.
Users report that a query that filters on OrderDate is taking an exceptionally long time. You discover
that an index named IX_OrderDate on the CustomerOrder table is heavily fragmenteD.
You need to improve the performance of the IX_OrderDate index. The index should remain online
during the operation.
Which Transact-SQL command should you use?

A.
ALTER INDEX IX_OrderDateON CustomerOrderDISABLE

B.
ALTER INDEX IX_OrderDateON CustomerOrderENABLE

C.
ALTER INDEX IX_OrderDateON CustomerOrderREORGANIZE

D.
ALTER INDEX IX OrderDateON CustomerOrderREBUILD