You are creating a Windows Forms application by using the .Net Framework 3.5.You create an instance of a Backgroundworker component named backgroundWorker1 to process operations that take a long time.You discover that when the application attempts to report the progress，you receive a System.InvalidOperationException exception when executing thebackgroundWorker1.ReportProgress method.You need to configure the BackgroundWorker component appropriately to prevent the application from generating exceptions. What should yo do？（） ["Set the Result property of the DoWorkEventArgs instance to True before you attempt to report the progress.","Set the CancellationPending property of backgroundWorker1 to True before you attempt to report the background process","Set the WorkerReportsProgress property of backgroundWorker1 to True before you attempt to report the background process.","Report the progress of the background process in the backgroundWorker1_ProgressChanged event."]
原发性下肢静脉曲张病因不包括（） ["先天性静脉壁薄弱","浅静脉瓣膜发育不良","经常参加游泳训练","长期从事负重劳动","长期站立工作"]
《规程》对矿井有害气体中一氧化碳最高允许浓度是（）。 ["0.00024%","0.0024%","24"]
简述植物对低温的适应。
农村居民独生子女父母奖励金由（），县（市、区）财政给予适当补助。 ["市（设区）财政支付","乡（镇）财政支付","村民委员会支付","乡镇企业"]
杠杆定律与重心法则有什么关系？在三元相图的分析中怎样运用杠杆定律和重心法则？
