Which code segment should you use?

You need to update the CreateMonthlyTotalsReports() method to use database transactions. Which code segment should you use?
A. SqlConnection.BeginTransaction(lsolationLevel.Chaos);
B. SqlConnection.BeginTransaction(lsolationLevel.Serializable);
C. SqlConnection.BeginTransaction(lsolationLevel.ReadCommitted);
D. SqlConnection.BeginTransaction(lsolationLevel.ReadUncommitted);