用"is","am","are"造过去式.例:I am ill today--I was ill yesterday--

1 I am late today--I was late yesterday--You were late yesterday
2 He is in Beijing now--He was in Beijing yesterday--They were all in Beijing yesterday
3 The pen is on the desk--The pen was on the desk just now--The pens were on the desk just now
4 This is my book--It was my book,but I lost it yesterday--These were all my books.
5 Is the light on?--Was the light on when you left the room?--Were the lights on when you left the room?