You have an SQL query that takes one minute to execute. You use the following code segment to execute the SQL query asynchronously.Dim ar As IAsyncResult = cmd.BeginExecuteReader（　）You need to execute a method named DoWork（　） that takes one second to run while the SQL query is executing. DoWork（　） must run as many times as possible while the SQL query is executing. Which code segment should you use?（）

• A、While ar.AsyncWaitHandle Is Nothing DoWork()End Whiledr = cmd.EndExecuteReader(ar)
• B、While Not ar.IsCompleted DoWork()End Whiledr = cmd.EndExecuteReader(ar)
• C、While T hread.CurrentThread.ThreadState = ThreadState.Running DoWork()End Whiledr = cmd.EndExecuteReader(ar)
• D、While Not ar.AsyncWaitHandle.WaitOne() DoWork()End Whiledr = cmd.EndExecuteReader(ar)