Which Transact-SQL statement or statements should you run?

You are designing a stored procedure for a database named DB1.
The following requirements must be met during the entire execution of the stored procedure:
• The stored procedure must only read changes that are persisted to the database.
• SELECT statements within the stored procedure should only show changes to the data that are made by the stored procedure.
You need to configure the transaction isolation level for the stored procedure.
Which Transact-SQL statement or statements should you run?
A. SET TRANSACTION ISOLATION LEVEL READ UNCOMMITED
ALTER DATABASE DB1 SET READ_COMMITED_SNAPSHOT ON
B. SET TRANSACTION ISOLATION LEVEL READ COMMITED
ALTER DATABASE DB1 SET READ_COMMITED_SNAPSHOT OFF
C. SET TRANSACTION ISOLATION LEVEL SERIALIZABLE
D. SET TRANSACTION ISOLATION LEVEL READ UNCOMMITED ALTER DATABASE SET READ_COMMITED_SNAPSHOT OFF