Using modal verbs must, might, might not, may, may not, can, could or can't write the second sentence so that it has a similar meaning to the first sentence 2 I'm sure they are not at school now.
3 It's possible that the match will not start before seven.
4 I'm sure she thinks I am not very bright.
5 I know this isn't Robert he has gone on holiday to Spain. 6 I'm certain the car keys are somewhere in the kitchen.
7 Perhaps the teacher will give us our homework back tomorrow.