Rewrite these sentences, using IN, At, Under or On

IV_Rewrite these sentences, using IN, At, Under or On
1) Keith certainly can't be held responsible for the accident
-> .....
2) The children themselves are not in any way to blame for the disaster
->............
3) The existence of extraterrestrial is not confirmed by thy report 
->.......
4) I was never shown how to operate the machinery
->......
5)  He necer suspected that she was a witch
->..........
6) There has never been a time when the English language was not in a state of change
->............