Which Transact-SQL statement should you include at the beginning of the stored procedure?

You are writing a set of queries against a FILESTREAM-enabled database.
You create a stored procedure that will update multiple tables within a transaction.
You need to ensure that if the stored procedure raises a runtime error, the entire transaction
is terminated and rolled back.
Which Transact-SQL statement should you include at the beginning of the stored
procedure?

A.
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE

B.
SET XACT_ABORT OFF

C.
SET TRANSACTION ISOLATION LEVEL SNAPSHOT

D.
SET IMPLICIT_TRANSACTIONS ON

E.
SET XACT_ABORT ON

F.
SET IMPLICIT TRANSACTIONS OFF

Explanation:
Reference:
http://msdn.microsoft.com/en-us/library/ms188792.aspx