You are developing a Windows Communication Foundation (WCF) service that allows customers to update financial data.
The service contract is defined as follows. (Line numbers are included for reference only)
01 [ServiceContract]
02 public interface IDataUpdate
03 {
04 [OperationContract]
05 [TransactionFlow(TransactionFlowOption.Mandatory)]
06 void Update(string accountNumber, double amount);
07 }
08
09 class UpdateService : IDataUpdate
10 {
11 [OperationBehavior(TransactionScopeRequired = true, TransactionAutoComplete = false)]
12 public void Update(string accountNumber, double amount)
13 {
14 ...
15 }
16 }
17
You need to ensure that the service is invoked within the transaction.
What should you do?（）

A. Replace line 01 with the following code [ServiceContract(SessionMode = SessionMode.NotAllowed)]
B. Replace line 01 with the following code [ServiceContract(SessionMode = SessionMode.Required)]
C. Call the Invoke method of the form and supply a delegate.
D. Call the BeginInvoke method of the form and supply a delegate.