[单选] 燃气锅炉房的烟气冷凝回收会（）锅炉热效率。

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?（） While ar.AsyncWaitHandle Is Nothing DoWork()End Whiledr = cmd.EndExecuteReader(ar)。 While Not ar.IsCompleted DoWork()End Whiledr = cmd.EndExecuteReader(ar)。 While T hread.CurrentThread.ThreadState = ThreadState.Running DoWork()End Whiledr = cmd.EndExecuteReader(ar)。 While Not ar.AsyncWaitHandle.WaitOne() DoWork()End Whiledr = cmd.EndExecuteReader(ar)。 水泥密度的测定过程中，将无水煤油注入李氏比重瓶时，液面应在0mL至1mL之间，读数以弯液面下部为准。 你在 Certkiller.com 做应用程序的开发工作。，Certkiller.com，让你在开发应用程序处理Certkiller.com 停车场通行证。应用程序必须存储和检索使用车辆识别号码 (VIN) 的车辆信息。您需要使用正确的代码，以确保类型安全。你应该做什么？（） 。 。 。 。 万能人寿保险 婴儿味觉敏感度下降，矮小、消瘦、免疫功能低下可能是缺乏（）。 铁。 锌。 碘。 锰。 燃气锅炉房的烟气冷凝回收会（）锅炉热效率。