Which Transact-SQL statement should you use?

You develop a Microsoft SQL Server 2012 server database that supports an application.
The application contains a table that has the following definition:
CREATE TABLE Inventory (
ItemID int NOT NULL PRIMARY KEY,
ItemsInStore int NOT NULL,
ItemsInWarehouse int NOT NULL)
You need to create a computed column that returns the sum total of the ItemsInStore and ItemsInWarehouse values for each row.
The new column is expected to be queried heavily, and you need to be able to index the column.
Which Transact-SQL statement should you use?

A.
ALTER TABLE Inventory
ADD TotalItems AS ItemslnStore + ItemsInWarehouse

B.
ALTER TABLE Inventory
ADD TotalItems AS ItemsInStore + ItemsInWarehouse PERSISTED

C.
ALTER TABLE Inventory
ADD TotalItems AS SUM(ItemsInStore, ItemsInWarehouse) PERSISTED

D.
ALTER TABLE Inventory
ADD TotalItems AS SUM(ItemsInStore, ItemsInWarehouse)

Explanation:
http://msdn.microsoft.com/en-us/library/ms174979.aspx