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.
Which Transact-SQL statement should you use?

A.
ALTER TABLE Inventory
ADD TotalItems AS ItemsInStore + ItemsInWarehouse

B.
ALTER TABLE Inventory
ADD ItemsInStore – ItemsInWarehouse = TotalItemss

C.
ALTER TABLE Inventory
ADD TotalItems = ItemsInStore + ItemsInWarehouse

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

Explanation:
Reference:
http://technet.microsoft.com/en-us/library/ms190273.aspx