A.[ServiceContract]public Class Service1{[Operation Contract]double Add（double n1，double n2）}
B.[ServiceContract]public Interface IService1{[Operation Contract]double Add（double n1，double n2）}
C.[ServiceContract]public Interface IService1{double Add（double n1，double n2）}
D.public Interface IService1{[Operation Contract]double Add（double n1，double n2）}

A.CancellationTokenSource
B.CancellationToken
C.TaskCreationOption
D.TaskStatus

A.Lambda
B.Action
C.Func
D.Tuple

A.任務(wù)無(wú)法取消
B.在基于任務(wù)的編程模型中，并行和異步都是通過(guò)任務(wù)來(lái)實(shí)現(xiàn)的
C.await運(yùn)算符和同步編程的最大區(qū)別是：異步等待任務(wù)完成時(shí)，既不會(huì)繼續(xù)執(zhí)行其后面的代碼，也不會(huì)影響用戶(hù)對(duì)UI界面的操作
D.Task.Delay方法只能用于異步等待任務(wù)，等待過(guò)程中不會(huì)影響UI操作，仍能保持界面操作流暢

A.async
B.Action
C.Func
D.await