There is there are there has been there have been introductory it

It/This – аввал айтиб утилган ёки курсатилган ибора, эргаш гап ёки феълни билдириши мумкин:

He smokes in bed, though I don’t like it. (It = his smoking bed.)
He suggested flying, but I thought it would cost too much. (It=flying)
I’m resigning. I can’t stand it (= my resigning) any longer.
The building is on fire. It (= that the building is on fire) is terrible.
Now they are able to do it by themselves. Oh it (= that they are able to do it by themselves) is
good.
Tom helped write my paper and I really appreciate it (= his helping).
He is trying much t get the scholarship. But I think it (his trying) is vain.

• 
  It – шахссиз гаплар учун эга вазифасини бажариши мумкин:
  

It seems... It appears... It looks... It happens...

It seems no one really knows where he is going.

It happened to be a nice day.
It appears that there have been some changes in the continent.
It appears the boys are innocent.
It looks as if (=худди) he was poisoned.
It happened that the new employee was the person who had come to the
manager earlier.