为什么用have been completed而不用are completed?All the preparations for the discussion have been completed and we are ready to start.

there have been great changes为什么用have been i have neve been late for work为什么用been I have been sick since yesterday.中have been 是什么是时态为什么要用been. 英语翻译为什么用have been 不懂 Nothing could have been more annoying.翻译并解释为什么用could have been 他们结婚十年了 They have been married for ten years 为什么要用have been have been encouragement for me for many years have been encouragement的含义为什么用encouragement you have done me a great service.为什么用have done,为什么不用have been have been doing 为什么还有 have been deadj the room is in the terrible mess ,it can not have been cleaned .为什么用can not have been为什么不用should not have been I have been to Beijing twice 为什么用现在完成时 1.Gansu,（）has been reported,will have continuous rain in the next few...1.Gansu,（）has been reported,will have continuous rain in the next few days.A.which B.where C.as D.that2.The car damaged in the accident can not be used unless（）comple I have been busy yesterday afternoon为什么要用have been busy而不用have busy主要想问的是什么时候现在完成时里动词前要用been,也就是have been ...例如还有 ：She has been sick since last month. how long have you been like this中为什么用been How many times have you been to Beijing?中为什么用的是been Have you ever been to HangZhou为什么用been 不用went 呢 The Smiths have been here for over ten years 为什么用“been here” It must have been drop somewhere in the 为什么用been